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1

Structure of dental gallium alloys.  

PubMed

The interest in gallium alloys as a replacement for amalgam has increased in recent years due to the risk of environmental pollution from amalgam. Alloy powders with compositions close to those for alloys of amalgam are mixed with a liquid gallium alloy. The mix is condensed into a prepared cavity in much the same way as for amalgam. The aim of the present work was to study the structure of: (1) two commercial alloy powders containing mainly silver, tin and copper, and (2) the phases formed by mixing these powders with a liquid alloy of gallium, indium and tin. One of the alloy powders contained 9 wt% palladium. Cross-sections of cylindrical specimens made by these gallium mixes were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Discrete grains of the following phases were found to be present in both gallium alloys: hexagonal Ag2Ga, tetragonal Cu(Pd)Ga2, cubic Ag9In4 and tetragonal beta-Sn. Indications of hexagonal or orthorhombic Ag2Sn were found in the remaining, unreacted alloy particles. In the palladium-containing alloy the X-ray reflections indicate a minor fraction of cubic Cu9Ga4 in addition to the Cu(Pd)Ga2 phase. Particles of beta-Sn are probably precipitated because Sn-Ga phases cannot be formed according to the binary phase diagram. PMID:8805980

Herø, H; Simensen, C J; Jørgensen, R B

1996-07-01

2

[A basic study on gallium alloys for dental restorations. Improvement of liquid gallium alloy].  

PubMed

This study was made to compare the physical and chemical properties of amalgam with those of gallium alloy in which the invented liquid alloy containing the three fundamental components of Ga-Sn-In or Ga-Sn-In-Ag were used instead of mercury. Experiment 1. The physical and chemical properties were investigated after the liquid gallium alloy and high copper amalgam powder were mixed. The following results were obtained; 1) The invented gallium alloy group showed expansion in dimensional changes immediately after mixing. This alloy group showed the same compressive and diametral tensile strength as those in amalgam after 7 days. 2) This alloy group showed slightly more corrosion weight loss in 0.05% HCl and 1% lactic acid solutions than that in amalgam, but this alloy group showed the same corrosion weight loss in 1% NaCl solution and artificial saliva as in amalgam. Also this alloy group showed more discoloration (delta E, NBS) in 0.1% Na2S solution than that in amalgam, but this showed the same degree of discoloration in artificial saliva. Experiment 2. The physical and chemical properties were investigated after the same liquid gallium alloy and Ag-Pd-Sn-Cu-Zn alloy powder were mixed. The following results were obtained; 1) The invented gallium alloy group showed expansion in dimensional changes immediately after mixing. This showed superior quality in compressive and diametral tensile strength as compared with those of amalgam. 2) The invented gallium alloy showed slightly more corrosion weight loss in 0.05% HCl and 1% lactic acid solutions than that in amalgam, but this alloy group showed the same corrosion weight loss in 1% NaCl solution and artificial saliva as in amalgam. Also this alloy group showed more discoloration (delta E, NBS) in 0.1% solution than that in amalgam, but it was the same in artificial saliva. PMID:2488904

Yada, I

1989-01-01

3

Electrohydrodynamic Spraying of Gallium-Indium Alloy.  

National Technical Information Service (NTIS)

The electrical atomization of a liquid eutectic alloy of Gallium and Indium was investigated in a vacuum. A time-of-flight mass spectrometer was used to determine the drop characteristics in the spray. The atomization, per se, results from the instability...

D. S. Swatik

1967-01-01

4

Gallium alloy films investigated for use as boundary lubricants  

NASA Technical Reports Server (NTRS)

Gallium alloyed with other low melting point metals has excellent lubricant properties of fluidity and low vapor pressure for high temperature or vacuum environments. The addition of other soft metals reduces the corrosivity and formation of undesirable alloys normally found with gallium.

1966-01-01

5

Optical microcharacterization of gallium nitride and indium gallium nitride alloys  

NASA Astrophysics Data System (ADS)

Gallium Nitride (GaN) and its alloys are attractive candidate materials for light-emitting applications in the visible and ultraviolet regions of the electromagnetic spectrum. The wide direct bandgap of the III-nitrides makes them very efficient light-emitters and their short bond length makes them extremely robust and durable. During the last decade, there have been rapid strides in the development of these materials and several devices based on them have already been commercialized. However, there are many issues with these materials that remain to be solved. This dissertation focuses on two main issues: one, the properties of Indium Gallium Nitride (InGaN) and two, the effect of dislocations on material properties. InGaN alloys are very difficult to grow, and a principal effort in the research community today is to achieve growth of high-quality films with high indium compositions. In order to overcome the problems associated with the growth of InGaN, it is important to gain an understanding of the basic nature of the material. In this work, the microstructure and electronic properties of thick InGaN epilayers has been studied. This enables investigation of material properties free of quantum confinement effects. The electronic properties of InGaN were observed to strongly vary with indium composition. Dislocations in the underlying GaN layer act as nucleation sites for phase separation and have a significant effect on material properties. The dislocation density was also found to play an important role in determining the strain relaxation mechanism in InGaN epilayers. The effect of dislocations on materials properties is an interesting problem that is being studied in great detail. In this study, it was found that the electronic properties in epitaxial lateral overgrowth of GaN are strongly dependent on the growth direction and unrelated to dislocation density. The properties appeared to be determined by point defects whose incorporation depends on the growth surface. Luminescence characteristics were studied across threading dislocations in semi-insulating GaN and were found to be closely related to the electrostatic potential measured by electron holography. This work has investigated important materials issues in GaN and InGaN and has contributed in developing a basic understanding of these materials.

Srinivasan, Sridhar

6

Machining of iron–gallium alloy for microactuator  

Microsoft Academic Search

We study the micromachining of iron–gallium alloy for use in a microactuator. Iron–gallium (Galfenol) is an iron-based magnetostrictive material with magnetostriction exceeding 200ppm, Young's modulus of 70GPa, and distinctive ductile and machinable properties. An actuator made by small Galfenol component therefore should be simple, robust against external forces and drivable at low voltage. A rod of Galfenol (Fe81.6Ga18.4) prepared by

T. Ueno; E. Summers; T. Higuchi

2007-01-01

7

Gallium arsenic nitride and gallium arsenic bismuth novel optoelectronic alloys  

NASA Astrophysics Data System (ADS)

Forming an alloy from two dissimilar but isovalent semiconductor compounds, A-B and A-C, can form what is called an isoelectronic alloy if two distinctive characteristics are observed: (1) the A-B1-xCx, alloy has a well-defined fundamental band gap as well as other electronic band edges, and (2) at low concentrations (x << 1%) the isovalent impurity C replacing B traps a charge carrier. In this thesis, two GaAs-based isoelectronic alloys are investigated experimentally. The first one, GaAsN, is formed by replacing As by a very small atom attractive to electrons whereas the second, GaAsBi, is formed by replacing As by a very large atom attractive to holes. For GaAsN, the new optical transitions, forbidden in GaAs, originate from the splitting of the quadruply degenerate conduction band at L6c, and become allowed due to the strong perturbation of the potential of N to the band structure of GaAs. The mutual repulsion between the split singlet state and the bottom of the conduction band is the origin of the unusual and non monotonic band gap dependence observed for this alloy. For the first time, a pseudo-donor isoelectronic alloy is identified. First, the band gap energy dependence of GaAsBi on Bi concentration is unusually larger than that observed from other isovalent semiconductor alloys. Similar to the case of GaAsN, this effect results from the strong perturbation caused by Bi on the periodicity of the GaAs regular lattice, lowering the symmetry and redefining the interactions within the band structure. Second, Bi-related excitonic bound states are observed and are likely composed of at least two Bi atoms. The Bi bound state should be located at higher energy, close to the valence band edge or resonant with the valence band. The final aspect relates to the photoluminescence from GaAs doped with a very low N concentration. Using optical spectroscopy with diffraction limited spatial resolution, we have measured the luminescence from single impurity centers formed by two neighboring N atoms in GaAs. Selectively studying individual centers makes it possible to unveil their otherwise concealed polarization anisotropy, analyze their selection rules, identify their particular configuration, map their spatial distribution, and demonstrate the presence of a diversity of local environments.

Francoeur, Sebastien

8

Gallium-induced magnesium enrichment on grain boundary and the gallium effect on degradation of tensile properties of aluminum alloys  

Microsoft Academic Search

By applying a controlled amount of gallium (3 mg or 5 mg) to double-notched samples, the effects of the gallium on the grain\\u000a boundary chemistry and tensile properties of AA6061-T4 alloy were investigated. Commercial-purity aluminum AA1050 was used\\u000a for comparison to determine whether alloying elements would correlate with Ga-induced embrittlement and to elucidate the physical\\u000a reason that governed the occurrence

Jun-Yen Uan; Cheng-Chia Chang

2006-01-01

9

Dental gallium alloy composites studied by SEM and TEM.  

PubMed

Analytical scanning and transmission electron microscopy (SEM and TEM) studies of dental gallium alloys have been carried out. The Ga alloys were made by triturating a LU powder (Ag-Sn-Cu rich alloy powder) and a GF powder (Ag-Sn-Cu-Pd rich alloy powder) with a liquid Ga alloy containing Ga, In and Sn. The dental materials were found to be composites consisting of remaining, undissolved particles from the Ag-based alloy powders in a matrix of reaction products with the Ga alloy. SEM studies have been carried out to give an overview of the composites. The distribution of the elements was found by the X-ray mapping technique. The phases in the matrix and the remaining alloy particles have been identified by electron diffraction, high-resolution electron microscopy and energy-dispersive X-ray spectroscopy. The following phases were identified in the LU alloy: orthorhombic Ag3Sn, cubic Ag9In4, tetragonal beta-Sn and hexagonal Ag2Ga. In addition to these well-known phases Ga-rich regions were observed consisting of an intergrowth of tetragonal CuGa2 and one of the cubic gamma-Cu9Ga4 phases. In addition to these phases cubic Ga7Pd3 was found in the GF alloy. The anomalous setting expansion of the GF alloy may be explained by the presence of Ga7Pd3. PMID:9088084

Gunnaes, A E; Olsen, A; Herø, H

1997-02-01

10

Fundamental studies of the metallurgical, electrical, and optical properties of gallium phosphide and gallium phosphide alloys  

NASA Technical Reports Server (NTRS)

Abstracts, bibliographic data, oral presentations, and published papers on (1) Diffusion of Sulfur in Gallium Phosphide and Gallium Arsenide, and (2) Properties of Gallium Phosphide Schottky Barrier Rectifiers for Use at High Temperature are presented.

1972-01-01

11

Development and modeling of iron-gallium alloys  

NASA Astrophysics Data System (ADS)

Alloys of iron substituted with non-magnetic gallium (Galfenol) appear promising as mechanically robust actuator/sensing materials. They offer desirable properties including tensile strengths and magnetostrictive strains, respectively, on the order of 100 MPa and 100 x 10-6. To advance the understanding of these materials, this dissertation examines the alloys' magnetic and mechanical response as a function of applied magnetic field, mechanical stress, temperature, stoichiometry and crystallographic morphology. Characterizations of the alloys' single-crystal magneto strictive, elastic and plastic properties are used to facilitate the development and modeling of polycrystalline forms of the material having preferred crystallographic orientations (i.e. texture). The polycrystalline forms have potentially higher production yields and superior mechanical properties over those of single crystals. Irongallium alloys textured by different manufacturing processes reveal which production methods result in the most desirable magnetostrictive and mechanical performance envelopes. Growth and deformation processing techniques such as directional solidification, extrusion, forging and rolling were used to impart a variety of different texture distributions. Single-crystal tensile test were used to determine the material's elastic constants, yield stress, slip systems and their critical resolved shear stress as well as ultimate strength and percent elongation. Observations of the single-crystal alloys' remarkable in-plane auxeticity (or negative Poisson's ratio) and quadratic correlations of the Poisson's ratio magnitude to the level of gallium substitution are reported. Potential applications based on in-plane auxeticity are explored. Elastic properties, as determined from tensile testing on single-crystal specimens, provided the basis for the development and use of a M&barbelow;agnetostrictive M&barbelow;icromechanics F&barbelow;inite-E&barbelow;lement M&barbelow;odel (MMFEM) that captured the coupled magnetic and mechanical behavior of polycrystalline specimens. The MMFEM correctly reflects the bulk magnetostrictive capability of polycrystalline specimens having well-characterized texture distributions and provides a tool for predicting the magnetostrictive performance of textures yet to be produced.

Kellogg, Rick Allen

12

Shear strengths of a gallium alloy bonded to human enamel following nine different surface treatments  

Microsoft Academic Search

Objective: Gallium and indium-containing alloys have demonstrated an ability to wet and bond to many types of materials including enamel. The purpose of this study was to evaluate and compare the bond strengths of a gallium-and-indium-containing alloy and a dental amalgam to human enamel surfaces.Method: A flat enamel bonding surface was created by slicing recently extracted human molars with a

J Claire; P. T Williams

2001-01-01

13

Thermodynamic studies of gallium--indium liquid alloys by solid state electrochemistry with oxide electrolytes  

Microsoft Academic Search

The activity of gallium in Ga--In liquid alloys was studied in a high temperature galvanic cell using calcia stabilized zirconia as an oxide electrolyte. The measured activity data for gallium in the Ga-In melts were used to calculate the interaction coefficient in the liquid alloy, which has the form ..cap alpha..\\/sub GaIn\\/ = In ..gamma..\\/sub Ga\\/\\/(1 --x\\/sub Ga\\/)² = 0.2862

Raymond Pong; Lee F. Donaghey

1976-01-01

14

Magnetostrictive bending micro-actuator using iron gallium-alloy  

NASA Astrophysics Data System (ADS)

We investigate a micro bending actuator based on unimorph, lamination of Galfenol (Iron-gallium alloy) and non-magnetic material. Galfenol C-shape yoke bonded with stainless plates (lamination) is wound coils, and is composed close magnetic loop with connected an iron plate. The magnetostriction in longitude direction is constrained by the stainless, thus, the laminations yield bending deformation with the current flowing. The advantage of the actuator is simple, compact and ease of assembling including winding coil, and high tolerance against bending, tensile and impact. We machined the yoke from a plate of 1mm thickness of polycrystalline Galfenol (Fe 81.4Ga 18.6 Research grade) using ultra high precision cutting technique. The prototype, thickness of 1mm and length of 10mm, was observed the displacement 13?m and 1st resonance at 1.6 kHz, and the high bending (tensile) tolerance withstanding suspended weight of 500g.

Ueno, Toshiyuki; Higuchi, Toshiro

2007-04-01

15

Miniature spherical motor using iron-gallium alloy (Galfenol)  

NASA Astrophysics Data System (ADS)

We propose a miniature spherical motor using iron-gallium alloy (Galfenol). This motor consists of four rods of Galfenol with square cross-section, a wound coil, a permanent magnet, an iron yoke and a spherical rotor placed on the edge of the rods. The magnetomotive force of the magnet provides bias magnetostriction for the rods and an attractive force that maintains the rotor on the rods. When currents of 180 deg phase difference flow in pairs of opposing coils, a torque is exerted on the rotor is by pushing (expansion) and pulling (contraction) of the rods. Rotation about a single axis is realized by a sawtooth current, such that the rotor rotates with slow expansion and slips at the rapid contraction. The motor can be fabricated at small sizes and driven with a low voltage, suitable for application as a microactuator for rotating the camera and mirror in endoscopes.

Ueno, Toshiyuki; Saito, Chihiro; Imaizumi, Nobuo; Higuchi, Toshiro

2008-05-01

16

Electron backscatter diffraction of plutonium-gallium alloys  

SciTech Connect

At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.

Boehlert, C. J. (Carl J.); Zocco, T. G. (Thomas G.); Schulze, R. K. (Roland K.); Mitchell, J. N. (Jeremy N.); Pereyra, R. A. (Ramiro A.)

2002-01-01

17

Separation of gallium and germanium in the dissolution of Ga-Ge alloys  

SciTech Connect

A mechanism was analyzed for the extraction of trace amounts of germanium from a gallium-germanium liquid alloy during dissolution in an alkaline peroxide solution. Expressions were obtained interrelating the process parameters, including surface area, volume of the contacting phases, degree of germanium extraction, and dissolution rate constants of gallium, germanium, and other metals - in all cases with repeated solvent replacements. The expressions satisfactorily represented the extraction of trace germanium in the system.

Gromov, V.V.; Bondarenko, G.P.

1985-11-01

18

Measurement of magnetic field dependent Young's modulus of iron-gallium alloy in flexural mode  

Microsoft Academic Search

Iron-Gallium alloys have demonstrated high compressive stress sensitivity (~ 30 T\\/GPa) along with considerable tensile strength (~ 515 MPa) and Young's modulus (~ 65 GPa) thus making them attractive materials for magnetostrictive sensors. In this work, four-point bending test was performed on single crystal Fe84Ga16 (Galfenol) under magnetic field to characterize its magneto-mechanical response in bending mode. The longitudinal and

Supratik Datta; Alison B. Flatau

2006-01-01

19

Liquid-phase gallium-indium alloy electronics with microcontact printing.  

PubMed

Liquid-phase electronic circuits are patterned on an elastomer substrate with a microcontact printer. The printer head dips into a pool of a liquid-phase gallium-indium alloy, e.g., eutectic gallium-indium (EGaIn) or gallium-indium-tin (Galinstan), and deposits a single drop on a silicone elastomer substrate. After patterned deposition, the liquid-phase circuit is sealed with an additional layer of silicone elastomer. We also demonstrate patterned deposition of the liquid-phase GaIn alloy with a molded polydimethylsiloxane stamp that is manually inked and pressed into an elastomer substrate. As with other liquid-phase electronics produced through needle injection or masked deposition, the circuit is elastically deformable and can be stretched to several times its natural length without losing electronic functionality. In contrast to existing fabrication techniques, microcontact printing and stamp lithography can be used to produce circuits with any planar geometric feature, including electrodes with large planar area, intersecting and closed-loop wires, and combs with multiple terminal electrodes. In air, the surface of the coalesced droplets oxidize to form a thin oxide skin that preserves the shape of the circuit during sealing. This first demonstration of soft-lithography fabrication with liquid-phase GaIn alloy expands the space of allowable circuit geometries and eliminates the need for mold or mask fabrication. PMID:23659455

Tabatabai, Arya; Fassler, Andrew; Usiak, Claire; Majidi, Carmel

2013-05-21

20

Development of highly magnetostrictive iron-gallium and iron-gallium-aluminum alloys  

NASA Astrophysics Data System (ADS)

Magnetostrictive materials that exhibit high mechanical strength, good ductility, large magnetostriction at low saturation fields under both no-load and high-imposed loading conditions, and low cost are of great interest for use in numerous magnetomechanical sensors and actuators. The main purposes of this research are to (i)identify such alloys based on Fe and relatively inexpensive alloying elements, (ii)develop low cost processing of these alloys using directional solidification and thermomechanical processing, and (iii)develop an understanding of how alloying elements and crystal structures influence magnetostriction in Fe. This work for the first time shows that BCC Fe-Ga based alloys show large low field magnetostriction. The magnetostriction values increase as Ga content increases and a preferred [001] crystallographic texture is approached. The values as high as 271 × 10-6 are obtained in the polycrystalline Fe-27.5 at.% Ga rod directionally grown at the rate of 22.5 mm/hour. These large values are obtained at very low applied fields (as low as 65 Oe) and with very small hysteresis. Alloys investigated here include Fe-x at.% Ga (x = 15, 20 and 27.5), Fe-y at.% Ga- (20-y) at.% Al (y = 0, 5, 10 and 15), Fe-13.75 at.% Ga- 13.75 at.% Al, Fe-15 at.% Al, Fe-15 at.% Al-4 at.% Co, Fe-15 at.% Ga-4 at.% Co, Fe-15 at.% Mo, Fe-20 at.% Re, Fe-20 at.% Rh and Fe-10 at.% Sn. A directional casting process involving solidification by rapid one-dimensional heat extraction produced rods with a weak [110] preferred orientation resulting in low magnetostriction. A directional growth process involving controlled crucible movement in a furnace down the temperature gradient resulted in rods with a preferred orientation approaching [001] direction and a large magnetostriction. Orientation imaging microscopy study of texture evolution showed that a low-cost thermomechanical processing sequence of hot rolling, two-stage warm rolling reduction of about 60-65% with 900°C intermediate anneal, and a texture anneal at 1150°C can produce a [001] textured polycrystalline (Fe85Ga15)99(NbC)1 alloy. Rolled alloys exhibited tensile strengths of 576-588 MPa, yield strengths of 470-485 MPa and elongations of 28-29.5%. Fe-Ga alloys possess an excellent combination of magnetostriction, magnetic and mechanical properties desirable in a magnetostrictive actuator/sensor material.

Srisukhumbowornchai, Nakorn

2001-10-01

21

[Studies on newly improved gallium alloy as dental restorative material, by addition of SiC whisker and titanium powder].  

PubMed

Studies on new gallium alloy using liquid alloy of Ga-Sn-In which was stable at room temperature and with Ag-Sn-Cu-Pd-Zn alloy as powder, were undertaken. Two kinds of gallium alloy by addition of SiC whisker and titanium powder were made on an experimental basis for the purpose of improving the property of this alloy (reinforced alloy). Physical properties such as compressive strength, diametral tensile strength, dimensional change and chemical properties such as discoloration, corrosion, quantitative analysis by Inductively Coupled Plasma were measured. Furthermore breakage surface of alloy after tensile test was observed with SEM. The effect of adding SiC whisker and titanium powder to gallium alloy was discussed and the conclusions were as follows; 1) Compressive strength: Initial strength decreased due to addition of SiC whisker and titanium powder. However, it showed a tendency to increase as time elapsed. It approached the same degree of compressive strength after 7 days. 2) Diametral tensile strength: The best results were obtained by addition of 1% SiC whisker to gallium alloy and the optimum trituration time was 13 seconds in this study. 3) Dimensional change: Expansion in the dimensional change was observed in all testing groups which was slightly over the limitation of ISO and ADA No.1 specification. 4) Discoloration: In the case with addition of titanium powder to gallium alloy, an improvement of discoloration was manifested in artificial saliva and 1% NaS, especially prominent in the former. The favorable results were obtained by addition of 10% titanium powder to gallium alloy for discoloration tolerance. 5) Corrosion: The corrosion was low in four kinds of test immersion liquid. The best results were obtained by addition of 10% titanium powder to gallium alloy. 6) Quantitative analysis by Inductively Coupled Plasma: The examined amount of Zn dissolved out from core composition was decreased due to addition of titanium powder. An improvement of amount in dissolution of Ga, Sn and In from matrix was recognized. 7) In physical and chemical experiment's results, it was judged that the addition of 0.5-0.7% SiC whisker and 5-10% titanium powder was useful. PMID:2488895

Kim, H W

1989-01-01

22

Clinical study of an experimental gallium containing alloy.  

PubMed

The possibility for the clinical application of an experimental restorative material, which is composed of an Ag-Sn-Cu-Pd spherical alloy and a Ga-In-Sn-Ag alloy, was examined by observing periodic changes during class I restoration. In all of the restorations tested, the surface texture and the marginal integrity had deteriorated after a period of one year. Therefore, it was concluded that this metallic plastic filling material couldn't overcome physical and chemical stresses in the mouth, as a result, some improvement is required before this material can be substituted for the high copper amalgam. PMID:2490588

Yamashita, T; Itoh, K; Wakumoto, S

1989-12-01

23

Czochralski growth of gallium indium antimonide alloy crystals  

SciTech Connect

Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub 1{minus}x}Sb{sub x}. Single crystals of Ga{sub 1{minus}x}In{sub x}Sb were grown with uniform compositions up to nearly 5 mole% InSb.

Tsaur, S.C.

1998-02-01

24

Magnetoelastic coupling in nickel manganese gallium ferromagnetic shape memory alloy  

NASA Astrophysics Data System (ADS)

NiMnGa alloys have attracted extensive attention because their ferromagnetic characteristic provides an additional degree of freedom to control both the shape memory effect and the multi-stage phase transformations in this Heusler system. Technically, along with the large magnetic-field-induced strains, NiMnGa alloys exhibit giant magnetocaloric effect due to their magnetic entropy changes associated with the coupled magnetostructural transitions. Fundamentally, a sequence of phase transformations, manifesting itself by a rich variety of physical anomalies on cooling to the martensitic transformation (MT) temperature TM, has been established. However, in comparison to the intensive studies of structural transformations, the magnetic properties of NiMnGa premartensite were hardly touched. The purpose of this research is to (i) investigate the temperature dependence of the magnetic driving force of martensitic NiMnGa, which is a critical factor to determine the actuation temperature window of this material; and (ii) understand the magnetoelastic coupling enhanced precursor effects, especially the unique magnetic behavior of NiMnGa premartensite. The singular point detection technique has been applied to determine the magnetic anisotropy constant K1 of a martensitic Ni49.0 Mn23.5Ga27.5 (wt%) crystal. As expected, K 1 increases with decreasing temperatures below TM of 276 K, following a magnetization power law K1(T)/K1(0)=(M s(T)/Ms(0))3. However, the force required to initiate twin boundary motion increases exponentially with decreasing temperature. The combination of both temperature dependences leads to a very restricted temperature window for magnetic actuation using this alloy. The premartensitic transformation has been established by means of neutron powder diffraction and measurements of elastic constants of C44 and C'. The premartensitic phase has been verified by the stiffening of C 44 prior to the MT. The slope change of C' at TC positively confirms that the precursor phenomena are enhanced by the magnetoelastic coupling. Magnetic Ni49.0Mn23.5Ga27.5 premartensite is characterized by the coexistence of a finite dc magnetic susceptibility and a vanishing magnetocrystalline anisotropy, distinguishing bcc NiMnGa from the typical magnetic soft materials. This property arises from the competition between the exchange forces of the host lattice and the strong local crystal fields stemming from the tweed.

Zhao, Peng

25

Measured iron-gallium alloy tensile properties under magnetic fields  

NASA Astrophysics Data System (ADS)

Tension testing is used to identify Galfenol material properties under low level DC magnetic bias fields. Dog bone shaped specimens of single crystal Fe100-xGax, where 17<=x<=33, underwent tensile testing along two crystalographic axis orientations, [110] and [100]. The material properties being investigated and calculated from measured quantities are: Young's modulus and Poisson's ratio. Data are presented that demonstrate the dependence of these material properties on applied magnetic field levels and provide a preliminary assessment of the trends in material properties for performance under varied operating conditions. The elastic properties of Fe-Ga alloys were observed to be increasingly anisotropic with rising Ga content for the stoichiometries examined. The largest elastic anisotropies were manifested in [110] Poisson's ratios of as low as -0.63 in one specimen. This negative Poisson's ratio creates a significant in-plane auxetic behavior that could be exploited in applications that capitalize on unique area effects produced under uniaxial loading.

Yoo, Jin-Hyeong; Flatau, Alison B.

2004-07-01

26

Further studies of the anodic dissolution in sodium chloride electrolyte of aluminium alloys containing tin and gallium  

Microsoft Academic Search

As part of a programme to develop a high power density, Al\\/air battery with a NaCl brine electrolyte, the high rate dissolution of an aluminium alloy containing tin and gallium was investigated in a small volume cell. The objective was to define the factors that limit aluminium dissolution in condition that mimic a high power density battery. In a cell

Maria Nestoridi; Derek Pletcher; Julian A. Wharton; Robert J. K. Wood

2009-01-01

27

Experimental evidence of Alfvén wave propagation in a Gallium alloy  

NASA Astrophysics Data System (ADS)

Experiments with a liquid metal alloy, Galinstan, are reported and show clear evidence of Alfvén wave propagation as well as resonance of Alfvén modes. Galinstan is liquid at room temperature and, although its electrical conductivity is not as large as that of liquid sodium or NaK, it has still been possible to study Alfvén waves, thanks to the use of intense magnetic fields up to 13 T. The maximal values of Lundquist number, around 60, are similar to that of the reference experimental study by Jameson [J. Fluid Mech. 19, 513 (1964)]. The generation mechanism for Alfvén waves and their reflection is studied carefully. Numerical simulations have been performed and have been able to reproduce the experimental results, despite the fact that the simulated magnetic Prandtl number was much larger than that of Galinstan. An originality of the present study is that a poloidal disturbance (magnetic and velocity fields) is generated, allowing us to track its propagation from outside the conducting domain, hence without interfering.

Alboussière, Thierry; Cardin, Philippe; Debray, François; La Rizza, Patrick; Masson, Jean-Paul; Plunian, Franck; Ribeiro, Adolfo; Schmitt, Denys

2011-09-01

28

The microstructural, mechanical, and fracture properties of austenitic stainless steel alloyed with gallium  

NASA Astrophysics Data System (ADS)

The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3, 6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility. Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement is partially responsible for increased embrittlement.

Kolman, D. G.; Bingert, J. F.; Field, R. D.

2004-11-01

29

Magnetostriction and corrosion studies in single crystals of iron-gallium alloys  

NASA Astrophysics Data System (ADS)

Iron-gallium alloys have an excellent combination of large low-field magnetostriction, good mechanical properties, low hysteresis, and relatively low cost. This dissertation focuses on the magneto striction and corrosion behaviors of single crystals of Fe-Ga alloys. In the first part, the variation of magnetostrictive coefficient: (3/2) lambda100, with composition and heat treatment conditions of Fe-Ga alloys, is examined. Single crystals with compositions Fe-15 at.% Ga, Fe-20 at.% Ga, and Fe-27.5 at.% Ga were obtained by (a) vertical Bridgman technique (DG) and (b) vertical Bridgman technique followed by long-term annealing (LTA) and quenching. Rapid quenching from a phase region improves the (3/2) lambda 100 value in these alloys. X-ray diffraction characterization showed for the first time the direct evidence of short-range ordering in these alloys. The second part reports the first study of alpha" ordering heat treatment on the elastic properties and magnetostriction of Fe-27.5 at.% Ga alloy single crystals. The elastic constants were measured using resonant ultrasound spectroscopy (RUS), and the elastic properties and magneto-elastic coupling constant were calculated. The (3/2) lambda100 and B1 values obtained for a phase were higher than alpha" phase. The third part examines the first study of corrosion behavior of as-cast FeGa and Fe-Ga-Al alloys in acidic, basic, and simulated seawater environments. Corrosion measurements were performed by Tafel scan and polarization resistance method and in general exhibited good corrosion resistance. The fourth part examines the first study of corrosion behavior of Fe-15 at.% Ga, Fe-20 at.% Ga, and Fe-27.5 at.% Ga DG and LTA alloy single crystals and the dependence of corrosion rates on the crystal orientations. The corrosion resistance was better in basic environments followed by simulated seawater and acidic environments. The fifth part examines the effect of magnetostriction on the corrosion behavior of [100]-oriented single crystal of Fe-20 at.% Ga alloy in acidic and simulated seawater solution, first study ever of this kind. Magnetostrictive strain introduced on the application of saturation magnetic field increased the corrosion rate of [100]-oriented Fe-20 at.% Ga alloy single crystal by 40% in 0.1M HCl and decreased the corrosion rate by 15% in 3.5 wt.% NaCl solution.

Jayaraman, Tanjore V.

30

Figures of merit of magnetostrictive single crystal iron-gallium alloys for actuator and sensor applications  

NASA Astrophysics Data System (ADS)

Energy density, magnetomechanical coupling factor and a dimensionless sensing gage factor of <1 0 0> oriented single crystal iron-gallium alloys with 16, 17.5, 19, 24.7 and 29 at% gallium were studied as functions of stress and magnetic field. To estimate these quantities, the samples were characterized under different quasi-static stress and magnetic field conditions. The experimental behavior was modeled using an energy-based non-linear approach. Both the experimental data and the model simulations were used to calculate material parameters such as magnetic permeability, piezo-magnetic strain coefficient ( d33), inverse piezo-magnetic coefficient (stress sensitivity, d* 33) and Young's modulus in the material. These quantities were used to obtain energy density, magnetomechanical coupling factor and sensing gage factor as functions of magnetomechanical conditions. Maximum energy density of around 3 kJ/m 3, magnetomechanical coupling factor higher than 0.75 and sensing gage factor on the order of 10 3 were calculated.

Datta, S.; Atulasimha, J.; Flatau, A. B.

2009-12-01

31

Ab initio study of gallium stabilized ?-plutonium alloys and hydrogen-vacancy complexes.  

PubMed

All-electron density functional theory was used to investigate ?-plutonium (?-Pu) alloyed with gallium (Ga) impurities at 3.125, 6.25, 9.375 atomic (at)% Ga concentrations. The results indicated that the lowest energy structure is anti-ferromagnetic, independent of the Ga concentration. At higher Ga concentrations (>3.125?at%), the position of the Ga atoms are separated by four nearest neighbor Pu-Pu shells. The results also showed that the lattice constant contracts with increasing Ga concentration, which is in agreement with experimental data. Furthermore with increasing Ga concentration, the face-centered-cubic structure becomes more stably coupled with increasing short-range disorder. The formation energies show that the alloying process is exothermic, with an energy range of -0.028 to -0.099?eV/atom. The analyses of the partial density of states indicated that the Pu-Ga interactions are dominated by Pu 6d and Ga 4p hybridizations, as well as Ga 4s-4p hybridizations. Finally, the computed formation energies for vacancy and hydrogen-vacancy complexes within the 3.125?at% Ga cell were 1.12?eV (endothermic) and -3.88?eV (exothermic), respectively. In addition, the hydrogen atom prefers to interact much more strongly to the Pu atom than the Ga atom in the hydrogen-vacancy complex. PMID:24832613

Hernandez, Sarah C; Schwartz, Daniel S; Taylor, Christopher D; Ray, Asok K

2014-06-11

32

Ab initio study of gallium stabilized ?-plutonium alloys and hydrogen–vacancy complexes  

NASA Astrophysics Data System (ADS)

All-electron density functional theory was used to investigate ?-plutonium (?-Pu) alloyed with gallium (Ga) impurities at 3.125, 6.25, 9.375 atomic (at)% Ga concentrations. The results indicated that the lowest energy structure is anti-ferromagnetic, independent of the Ga concentration. At higher Ga concentrations (>3.125?at%), the position of the Ga atoms are separated by four nearest neighbor Pu–Pu shells. The results also showed that the lattice constant contracts with increasing Ga concentration, which is in agreement with experimental data. Furthermore with increasing Ga concentration, the face-centered-cubic structure becomes more stably coupled with increasing short-range disorder. The formation energies show that the alloying process is exothermic, with an energy range of ?0.028 to ?0.099?eV/atom. The analyses of the partial density of states indicated that the Pu–Ga interactions are dominated by Pu 6d and Ga 4p hybridizations, as well as Ga 4s–4p hybridizations. Finally, the computed formation energies for vacancy and hydrogen–vacancy complexes within the 3.125?at% Ga cell were 1.12?eV (endothermic) and ?3.88?eV (exothermic), respectively. In addition, the hydrogen atom prefers to interact much more strongly to the Pu atom than the Ga atom in the hydrogen–vacancy complex.

Hernandez, Sarah C.; Schwartz, Daniel S.; Taylor, Christopher D.; Ray, Asok K.

2014-06-01

33

Micromagnetostrictive vibrator using a U-shaped core of iron-gallium alloy (Galfenol)  

NASA Astrophysics Data System (ADS)

A micromagnetostrictive vibrator using a U-shaped core made of iron-gallium alloy (Galfenol) was investigated. The vibrator consists of a Galfenol core, with a 1 mm2 cross section, a length of 5.8 mm, and a 0.3 mm separation between the prongs of the ``U,'' driving coils, and an iron yoke to close the magnetic loop. The Galfenol vibrator is superior to the PZT type in its high mechanical strength, low drive voltage requirements, and wide temperature operating range, and compared to our previous cylindrical type vibrator has a simpler construction and higher bandwidth. A displacement of 1.2 ?m (220 ppm) was verified for the prototype with a 5.8 mm long Galfenol core; the high magnetostriction >200 ppm is inherited from the stress-annealed Galfenol. The displacement was also maintained under a 21 MPa tensile stress (1.5 kg hanging weight). Incorporation of a Nd-B-Fe magnet into the magnetic circuit successfully shifted the operating point to the linear portion of the magnetostrictive curves. This biasing effect is useful in reducing the drive voltage.

Ueno, T.; Higuchi, T.; Saito, C.; Imaizumi, N.; Wun-Fogle, M.

2008-04-01

34

Kinetics of growth of indium gallium nitride alloys by MBE and development of polar and non-polar indium gallium nitride MQWs  

NASA Astrophysics Data System (ADS)

InGaN alloys and MQWs constitute the active region of light emitting diodes (LEDs) and lasers emitting in the visible part of the spectrum. In spite of the significant progress over the past several years, the physics related to the growth, structure and optical properties of these alloys is poorly understood. This has prevented the development of efficient emitters in the blue and green part of the spectrum where the indium mol fraction must exceed 15-20%. The difficulty with the growth of these alloys is partly related to solubility of InN in GaN at the usual growth temperatures and partly to significantly higher vapor pressure of nitrogen over InN than GaN. In this dissertation, I addressed the growth, the structure and the optical properties of InGaN alloys and QWs grown along polar and non-polar directions by plasma assisted MBE. The InGaN alloys were grown both in their nitrogen and gallium (indium) polar directions. The incorporation of Indium during growth was investigated in-situ by observing the evolution of reflected high energy electron diffraction (RHEED) patterns as a function of time, and ex-situ by x-ray diffraction studies. Conditions have been identified to grow nitrogen polar InGaN alloys in the entire alloy composition. On the other hand, the highest indium mol fraction achievable for Ga-polar growth was 30%. The difference between these two growth regimes was found to result from differences in the bonding of the two polarities. Study of the optical properties of these materials revealed Stoke's shifts in the emission spectra of 100 meV for N-polar films and up to 420 meV for Ga-polar films consistent with the microstructure identified for each. Polar InGaN MQWs were deposited on c-plane HVPE-grown GaN templates. The emission properties of these MQWs were correlated with various growth parameters by comparing the internal quantum efficiencies (IQEs), which varied from 0.5 to ˜30%. Furthermore, the role of dislocations as non-radiative recombination centers in these MQWs was investigated. Non-polar InGaN MQWs were deposited onto a-plane HVPE-grown GaN templates. These MQWs were found to have IQEs of ˜70%, a result consistent with the suppression of the quantum-confined-Stark-effect (QCSE). Prototype LED structures based on such MQWs were grown and fabricated into 800x800 mum devices. An output power of 14mW at 1A injection current was measured under bare die testing.

Abell, Joshua

35

Colloidal gallium indium oxide nanocrystals: a multifunctional light-emitting phosphor broadly tunable by alloy composition.  

PubMed

We demonstrate compositionally tunable photoluminescence in complex transparent conducting oxide nanocrystals. Alloyed gallium indium oxide (GIO) nanocrystals with variable crystal structures are prepared by a colloidal method throughout the full composition range and studied by different structural and spectroscopic methods, including photoluminescence and X-ray absorption. The structures and sizes of the GIO nanocrystals can be simultaneously controlled, owing to the difference in the growth kinetics of In(2)O(3) and Ga(2)O(3) nanocrystals and the polymorphic nature of both materials. Using the synthesized nanocrystal series, we demonstrate the structural and compositional dependences of the photoluminescence of GIO nanocrystals. These dependences, induced by the interactions between specific defect sites acting as electron donors and acceptors, are used to achieve broad emission tunability in the visible spectral range at room temperature. The nature of the photoluminescence is identified as donor-acceptor pair recombination and changes with increasing indium content owing to the changes in the energy states of, and interactions between, donors and acceptors. Structural analysis of GIO nanocrystals by extended X-ray absorption fine structure spectroscopy reveals that In(3+) occupies only octahedral, rather than tetrahedral, sites in the spinel-type ?-Ga(2)O(3) nanocrystal host lattice, until reaching the substitutional incorporation limit of ca. 25%. The emission decay dynamics is also strongly influenced by the nanocrystal structure and composition. The oxygen vacancy defects, responsible for the observed photoluminescence properties, are also implicated in other functional properties, particularly conductivity, enabling the application of colloidal GIO nanocrystals as integrated optoelectronic materials. PMID:21476551

Farvid, Shokouh S; Wang, Ting; Radovanovic, Pavle V

2011-05-01

36

Effect of tungsten and gallium on the structure and magnetic and mechanical properties of Fe-Cr-Co alloys  

NASA Astrophysics Data System (ADS)

Effects of the alloying additions of W and Ga, cold deformation, and regimes of heat treatment on the magnetic and mechanical properties of precipitation-hardening Fe-Cr-Co alloys have been investigated. It has been shown that the alloying with tungsten leads to a strengthening of the ? solid solution and an additional jumplike increase in strength after deformation and age hardening. The coercive force grows simultaneously with an increase in strength; the structure of the alloy in this case contains a large concentration of linear defects (dislocations), which indicates an important contribution of magnetoelastic energy to the formation of the high-coercivity state and of elastic strains to the increase in the strength properties. The character of fracture becomes brittle. The modifying of the alloy with gallium leads to an increase in plasticity due to the dispersion of the structure, formation of retained austenite in it, and formation of an interphase layer more uniform in composition. The character of fracture changes from brittle to brittle-ductile. A high-strength magnetically hard material has been obtained with H c = 90-125 A/cm, ? m = 120-130 G cm3/g, B r = 0.6-0.65 T, ?0.2 = 1300-1600 MPa, and ? = 2.0-4.6%.

Belozerov, E. V.; Uimin, M. A.; Ermakov, A. E.; Serikov, V. V.; Kleinerman, N. M.; Ivanova, G. V.

2008-11-01

37

Measurement of activity of gallium in solid Pt-Ga alloys by EMF method using zirconia as solid electrolyte  

SciTech Connect

EMF of galvanic cells with zirconia solid electrolytes was measured to determine the activity of gallium in solid Pt-Ga alloys in the temperature range 970--1,170 K in the entire composition range. Fe, Fe{sub x}O and/or Ga, Ga{sub 2}O{sub 3} mixtures were used as the reference electrode. Activity of Ga at 1,100 K changes largely in log scale in Pt-rich {alpha}-solid solution, GaPt{sub 3}, and GaPt phases; slightly in GaPt{sub 2}, Ga{sub 3}Pt{sub 2}, and Ga{sub 2}Pt phases; and moderately in Ga{sub 3}Pt{sub 5} and Ga{sub 7}Pt{sub 3} phases. The free energies of formation of each phase at 1,100 K are calculated from the experimental data.

Katayama, Iwao; Makino, Teruki; Iida, Takamichi [Osaka Univ., Suita, Osaka (Japan)

1995-08-01

38

Excessive thermodynamic properties of praseodymium in a gallium-indium alloy  

NASA Astrophysics Data System (ADS)

The equilibrium potentials of praseodymium-diluted homogeneous Pr-Ga-In alloys in a (Li-K-Cs)Cleut-based salt electrolyte were measured between 573-1073 K by the emf method. These potentials are used to calculate the activity coefficients of ?-praseodymium in liquid Ga-In eutectic alloys. PrIn3 alloy with well-known thermodynamic characteristics and without phase transitions in the temperature range 428-1483 K was employed as the reference electrode.

Mel'chakov, S. Yu.; Yamshchikov, L. F.; Ivanov, V. A.; Volkovich, V. A.; Osipenko, A. G.; Kormilitsyn, M. V.; Nagovitsyn, V. A.

2013-08-01

39

Thermodynamics of reaction of praseodymium with gallium-indium eutectic alloy  

NASA Astrophysics Data System (ADS)

Thermodynamic properties of Ga-In eutectic alloys saturated with praseodymium were determined for the first time employing the electromotive force method. The equilibrium potentials of the Pr-In alloys saturated with praseodymium (8.7-12.1 mol.% Pr) and Pr-Ga-In alloys (containing 0.0012-6.71 mol.% Pr) were measured between 573-1073 K. Pr-In alloy containing solid PrIn3 with known thermodynamic properties was used as the reference electrode when measuring the potentials of ternary Pr-In-Ga alloys. Activity, partial and excessive thermodynamic functions of praseodymium in alloys with indium and Ga-In eutectic were calculated. Activity (a), activity coefficients (?) and solubility (X) of praseodymium in the studied temperature range can be expressed by the following equations: lga?-Pr(In) = 4.425 - 11965/T ± 0.026. lg??-Pr(Ga-In) = 5.866 - 14766/T ± 0.190. lg??-Pr(Ga-In) = 2.351 - 9996/T ± 0.39. lg?Pr(Ga-In) = 3.515 - 4770/T ± 0.20.

Melchakov, S. Yu.; Ivanov, V. A.; Yamshchikov, L. F.; Volkovich, V. A.; Osipenko, A. G.; Kormilitsyn, M. V.

2013-06-01

40

Magnetostriction and texture development in binary and ternary iron-gallium-based alloys  

NASA Astrophysics Data System (ADS)

The rare earth-free bcc FeGa-based alloys have an excellent combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost. These alloys are attractive for use in numerous sensor and actuator devices. The first part of this dissertation examines the influence of partial substitutions of Ga with Al, Be, Si, Ge, and Sn and partial substitutions of Fe with Co and Ni. The work involved directional growth of [001] textured rods of these ternary alloys using a Vertical Bridgman process, X-ray diffraction analysis, magnetic property measurements using vibrating sample magnetometry, and magnetostriction measurements. It is shown that substitution of Ga with Al can be made in FeGa alloys in certain composition ranges without a reduction in magnetostriction, and the additions of Si, Ge, and Sn results in a sharp decrease of magnetostriction. The addition or substitute of Be, due to its smaller size than Fe, resulted in only a slight decrease of magnetostriction. Substitution of Fe with Ni and Co results in a significant decrease of the magnetostriction. The work also evaluated the elastic properties of Fe-x at. % Ga and Fe-(20-y) at. % Ga-y at. % Al polycrystalline alloys using resonant ultrasound spectroscopy. Young's modulus obtained for FeGa and FeGaAl alloys were in the range of 110 to 170 GPa which are several times that for Terfenol-D alloys. Thus, large-force delivery is possible from FeGa alloy based actuators even though saturation strain values are smaller than that of Terfenol-D. The second part of this work examined the development of an inexpensive thermomechanical processing method to obtain [001] textured polycrystalline Fe-15 at. % Ga alloys. The processing involved a sequence of controlled hot rolling, two-stage warm rolling with intermediate anneal, and texture anneal. Roll forces measured and the extent of reductions feasible indicated an excellent processability. Texture evolution during different stages of processing was examined using Orientation Imaging Microscopy to identify conditions that favor [001] texture development. The results indicate that addition of 1 mol.% NbC and controlled process conditions lead to a very strong [001] texture.

Mungsantisuk, Pinai

41

Effect of hydrogen and magnetic field on the mechanical behavior of magnetostrictive iron-gallium alloys  

NASA Astrophysics Data System (ADS)

Magnetostrictive Fe-Ga and other iron-based alloys are candidates for use in sensing, actuation and large-scale energy harvesting applications. Exposure to aqueous electrochemical environments is anticipated in some of these applications which could potentially introduce hydrogen into the alloy and cause severe ductility reduction due to hydrogen embrittlement. These alloys may also be simultaneously exposed to magnetic field. This study therefore examines the effect of hydrogen and magnetic field on the mechanical behavior of these alloys. This study could also provide an understanding of the relationship between hydrogen embrittlement and magnetoelastic behavior in these alloys. In this work, the effect of hydrogen and magnetic field on the fracture behavior of [100]-oriented Fe-17.5 at.% Ga alloy single crystals and polycrystalline Fe-15 at.% Ga alloy were examined. Three-point bend tests and tensile tests were used to study the fracture behavior. Tests were done in different conditions to understand the effect of hydrogen and magnetic field on the fracture behavior of these materials. Hydrogen loading was done by in-situ electrochemical charging and magnetic field was applied to the samples either by using Nd2Fe 14B permanent magnets or by using solenoid coils. Before doing the three-point bend test on the Fe-Ga single crystal samples, tests were done using high-strength AISI 4340 steel to optimize the testing procedures and parameters. In all cases, the samples tested with hydrogen charging show a drastic reduction in ductility and fracture stress values. In the case of [100]-oriented Fe-17.5 at.% Ga alloy single crystal samples tested with hydrogen charging, the presence of applied magnetic field increased the stress required for fracture and a corresponding increase in bending strain values. This is attributed to a decrease of the elastic modulus values on the application of magnetic field in this magnetostrictive alloy. The hydrogen embrittlement was characterized by a change in fracture surface from a ductile type fracture to a brittle cleavage type fracture. Acoustic emission signals collected during the test correspond to the fracture behavior.

Ramanathan, Meenakshisundaram

42

Structure and properties of dilute nitride gallium arsenic nitride alloy films  

Microsoft Academic Search

Dilute nitride semiconductor alloys are useful for a wide range of applications. A fundamental understanding of how various growth regimes affect the structural, optical and electronic properties is needed for further optimization of device performance. This thesis explores these issues in GaAsN. We investigated the temperature-dependent mechanisms of growth for GaAsN films. At low temperatures, limited adatom surface mobility leads

Matthew J. Reason

2006-01-01

43

Measurement of field-dependence elastic modulus of iron-gallium alloy using tensile test  

SciTech Connect

An experimental approach is used to identify Galfenol material properties under dc magnetic bias fields. Dog-bone-shaped specimens of single crystal Fe{sub 100-x}Ga{sub x}, where 18.6{<=}x{<=}33.2, underwent tensile testing along two crystallographic axis orientations, [110] and [100]. Young's modulus and Poisson's ratio sensitivity to magnetic fields and stoichiometry are investigated. Data are presented that demonstrate the dependence of these properties on applied magnetic-field levels and provide a substantial assessment of the trends in material properties for performance of alloys of different stoichiometries under varied operating conditions.

Yoo, Jin-Hyeong; Flatau, Alison B. [University of Maryland, College Park, Maryland 20742 (United States)

2005-05-15

44

Thermal cnductivity and Lorenz number of plutonium and plutonium-gallium alloys  

SciTech Connect

The thermal diffusivities of Pu, Pu-2.7 at. % Ga, Pu-3.5 at. % Ga, and Pu-6.6 at. % Ga were measured from 25/sup 0/C to around 500/sup 0/C using a laser flash technique and electronic data acquisition. Although the Lorenz number, L, of pure Pu is well below the Sommerfeld value, L/sub 0/, except for the ..cap alpha..-phase, L exceeds L/sub 0/ for the alloys at all temperatures and has a pronounced minimum around 200/sup 0/C. At the lower temperatures we attribute the excess to lattice conduction and at temperature above 200/sup 0/C the excess is attributed to an electronic component. The negative deviation of L from L/sub 0/ for pure Pu is ascribed to a reduction of the electron mobilities in those energy ranges where the 5f bands overlap the conduction bands.

Andrew, J.F.; Klemens, P.G.

1981-01-01

45

Evaluation of magnetostrictive shunt damper performance using Iron (Fe)-Gallium (Ga) alloy  

NASA Astrophysics Data System (ADS)

This study presents the possibility of dissipating mechanical energy with a proof-of-concept prototype magnetostrictive based shunt circuit using passive electrical components. The device consists of a polycrystalline galfenol (Fe-Ga alloy) strip bonded to a brass cantilever beam. Two brass pieces, each containing a permanent magnet, are used to mass load each end of the beam and to provide a magnetic bias field through the galfenol strip. The voltage induced in an induction coil closely wound around the cantilever beam captures the time rate of change of magnetic flux within the galfenol strip as the beam vibrates. The first bending-mode resonant frequency of the device was 69.42 Hz. To dissipate the electrical voltage from the device, a shunt circuit is attached. The effective mechanical impedance for the magnetostrictive shunt circuit is derived. The shunted model is specialized for two shunt circuits: the case of a resistor and that of a capacitance. The experimental results for both the resistive and capacitance shunt circuits validate the shunted magnetostrictive damping model for couple of cased of resistance and capacitance.

Yoo, JinHyeong; Murray, Andrew; Flatau, Alison B.

2014-04-01

46

Gallium--A smart metal  

USGS Publications Warehouse

Gallium is a soft, silvery metallic element with an atomic number of 31 and the chemical symbol Ga. The French chemist Paul-Emile Lecoq de Boisbaudran discovered gallium in sphalerite (a zinc-sulfide mineral) in 1875 using spectroscopy. He named the element "gallia" after his native land of France (formerly Gaul; in Latin, Gallia). The existence of gallium had been predicted in 1871 by Dmitri Mendeleev, the Russian chemist who published the first periodic table of the elements. Mendeleev noted a gap in his table and named the missing element "eka-aluminum" because he determined that its location was one place away from aluminum in the table. Mendeleev thought that the missing element (gallium) would be very much like aluminum in its chemical properties, and he was right. Solid gallium has a low melting temperature (~29 degrees Celsius, or °C) and an unusually high boiling point (~2,204 °C). Because of these properties, the earliest uses of gallium were in high-temperature thermometers and in designing metal alloys that melt easily. The development of a gallium-based direct band-gap semiconductor in the 1960s led to what is now one of the most well-known applications for gallium-based products--the manufacture of smartphones and data-centric networks.

Foley, Nora; Jaskula, Brian

2013-01-01

47

Development of gallium aluminum phosphide electroluminescent diodes  

NASA Technical Reports Server (NTRS)

Work done on the development of gallium aluminum phosphide alloys for electroluminescent light sources is described. The preparation of this wide band gap semiconductor alloy, its physical properties (particularly the band structure, the electrical characteristics, and the light emitting properties) and work done on the fabrication of diode structures from these alloys are broadly covered.

Chicotka, R. J.; Lorenz, M. R.; Nethercot, A. H.; Pettit, G. D.

1972-01-01

48

Effect of tungsten and gallium on the structure and magnetic and mechanical properties of Fe-Cr-Co alloys  

Microsoft Academic Search

Effects of the alloying additions of W and Ga, cold deformation, and regimes of heat treatment on the magnetic and mechanical\\u000a properties of precipitation-hardening Fe-Cr-Co alloys have been investigated. It has been shown that the alloying with tungsten\\u000a leads to a strengthening of the ? solid solution and an additional jumplike increase in strength after deformation and age\\u000a hardening. The

E. V. Belozerov; M. A. Uimin; A. E. Ermakov; V. V. Serikov; N. M. Kleinerman; G. V. Ivanova

2008-01-01

49

Complete wetting transitions at the liquid-vapor interface of gallium-bismuth alloys: Single-wavelength and spectroscopic ellipsometry studies  

NASA Astrophysics Data System (ADS)

Complete wetting transitions at the liquid-vapor interface of GaxBi1-x alloys ( xGa=0.915 , 0.88, 0.8, 0.67, and 0.57) have been investigated by ellipsometry. For this purpose we have developed a UHV apparatus equipped with an in situ phase modulation ellipsometer. The setup allows cleaning of the alloy surface under UHV conditions. Spectroscopic ellipsometry (0.8eV?h??4.65eV) at various constant temperatures and time-dependent measurements at a constant energy of 2.75eV , while the sample was continuously cooled down, are utilized. These complementary approaches promise access to the functional form of the wetting film thickness with temperature as complete wetting is approached. A multistage analysis is introduced to extract the film thickness from single-wavelength ellipsometry. For a careful analysis of the spectra, it was necessary to reinvestigate the complex dielectric functions of the pure components bismuth and gallium. The spectra of the alloys have been modeled using an effective medium approximation for the liquid Ga-Bi bulk phase covered by a film of liquid bismuth. In our particular sample geometry, the wetting film thickness grows from one or two atomic layers to about 30Åto50Å within a few K as one approaches the demixing regime. The data show the proposed logarithmic divergence of d , typical for short range interactions. In the temperature and composition range studied they do not agree with the functional form proposed for long range intermolecular interactions.

Dogel, S.; Nattland, D.; Freyland, W.

2005-08-01

50

Effects of Gallium and Mercury Ions on Transport Systems  

Microsoft Academic Search

Mercury was previously shown to exert toxic effects by influencing ion channels and transporters in the kidney and brain. Gallium alloys were suggested as less toxic restorative materials. To compare the toxicity of gallium ions with those of mercury ions, we applied gallium nitrate Ga(NO3)3 (0.1-100 ?M and mercuric chloride (HgCl2) (0.001-10 ?M) to Xenopus oocytes expressing mammalian ion channels

I. Moschen; K. Schweizer; C. A. Wagner; J. Geis-Gerstorfer; F. Lang

2001-01-01

51

Influence of dislocations and second phases on the magnetostrictive behavior of iron-gallium and other iron alloy single crystals  

NASA Astrophysics Data System (ADS)

Rare-earth-free Fe-Ga magnetostrictive alloys exhibit an excellent combination of large low-field magnetostriction, strength, ductility, wide operating temperature range, and low cost. Various observations in these and other alpha-Fe-based magnetostrictive alloys suggest that lattice strain modulations that are influenced by solute elements, near neighbor atomic environments around Fe atoms, coherent and incoherent precipitates, and structural defects such as dislocations likely play an important role in their magnetostrictive behavior. In the first part, the effect of dislocations on the magnetostriction of Fe-Ga single crystals was examined. The [001]- and [126]-oriented Fe-20 at.% Ga single crystal samples were deformed in a controlled way to introduce dislocation arrays with two different array geometries. Magnetostriction values showed a much lower decrease after deformation for the case of a [001]-oriented crystal, where eight different slip systems were operative and consequently eight different sets of dislocation arrays are expected. A drastic drop in magnetostriction measured along the sample axis is observed in the sample subjected to a small strain by deformation of a [126]-oriented crystal during which slip occurred on only one slip system. The nature of strain modulation introduced in this case was spatially asymmetric. The [126] deformation was accompanied by an acoustic emission during the formation of slip band. Transmission electron microscopy was carried out to examine the nature of dislocation distribution. The results show that the nature of strain modulation introduced by the dislocation arrays has a strong influence on the magnetostrictive behavior of magnetostrictive alloys. In the second part of this research, the effect of Mo addition to Fe was examined in detail. Addition of Mo to Fe increased the magnetostriction (3/2)lambda100 Fe very rapidly to 137 ppm at 10 at.% Mo, the highest value observed in these alloys. Further Mo additions decreased the magnetostriction. Magnetization data show a drastic drop in magnetization to 63 emu/gm for Fe-20 at.% Mo from 176 emu/gm for Fe-10 at.% Mo suggesting the formation large amounts of nonmagnetic second phase and reduction in total Fe content of the alloy. The drop in magnetostriction at higher Mo contents is associated with the formation of a second phase.

Saha, Biswadeep

52

Gallium Liquid Mirrors: Basic Technology, Optical-Shop Tests, and Observations  

NASA Astrophysics Data System (ADS)

We have investigated the use of gallium and low-melting-temperature gallium alloys for liquid mirrors. They have advantageous characteristics with respect to mercury. Simple knife-edge and Ronchi optical texts indicate that gallium mirrors ahve optical qualities similar to those of mercury mirrors. We have observed stars with a 1-m diameter liquid mirror telescope that used gallium- indium alloy. The instrument operated satisfactorily, within the limitations of a very simple telescope and instrumentation. Arguably, our most interesting finding is that the high melting temperature gallium isnot an obstacle since our experiments show that it is easy to supercool in large volumes and quite stable in the supercooled state. Furthermore, eutectic alloys of gallium have significantly lower melting temperatures than pure gallium and are also easy to supercool and stable in the supercooled state. The results of our experiments are encouraging and warrant further, more rigorous, continuation of this work. (SECTION: Astronomical Instrumentation)

Borra, E. F.; Tremblay, G.; Huot, Y.; Gauvin, J.

1997-03-01

53

Bismuth in gallium arsenide: Structural and electronic properties of GaAs 1- xBi x alloys  

NASA Astrophysics Data System (ADS)

The structural and electronic properties of cubic GaAs 1- xBi x alloys with bismuth concentration 0.0, 0.25, 0.50, 0.75 and 1.0 are studied using the 'special quasi-random structures' (SQS) approach of Zunger along with the generalized gradient approximation (GGA) and the Engel-Vosko generalized gradient approximation (EV-GGA). The lattice constant, bulk modulus, derivative of bulk modulus and energy gap vary with bismuth concentration nonlinearly. The present calculations show that the band gap decreases substantially with increasing bismuth concentration and that spin-orbit coupling influences the nature of bonding at high Bi concentrations.

Reshak, Ali Hussain; Kamarudin, H.; Auluck, S.; Kityk, I. V.

2012-02-01

54

Optical and electrical characterization of melt-grown bulk indium gallium arsenide and indium arsenic phosphide alloys  

NASA Astrophysics Data System (ADS)

Optical and electrical properties of bulk melt-grown ternary InAs 1-yPy and InxGa1-xAs polycrystals were investigated as functions of phosphorus and indium compositions and temperatures using the photoluminescence, Fourier transform infrared (FTIR) transmission spectrum, refractive index, and Hall-effect measurements. These ternary alloys were grown using the vertical Bridgman techniques. The as-grown undoped bulk ternary InAs1-yPy and InxGa1-xAs polycrystals have been found to exhibit n-type conductivity irrespective of the alloy compositions possibly due to residual impurities and native defects. In general, carrier concentrations and Hall mobilities increase with the indium composition for InxGa1-xAs, whereas they decrease with increasing phosphorus mole fraction for the InAs1-yPy sample. The FTIR spectra of all these ternary samples demonstrated good infrared transmission. A systematic measurement of photoluminescence was carried out in order to gain insight into the various radiative transitions in the InAs1-yPy and InxGa1-xAs crystals, which include the temperature, laser excitation power, and sample location dependent studies. The wavelength, temperature, and composition dependent refractive indices of InAs1-y Py and InxGa1-xAs were studied using minimum deviation and Michelson Fabry-Perot interferometry methods. The measured results of refractive indices, transport properties, bandgap energies, and optical transmissions are presented here as functions of alloy composition, temperature and photon energy for the first time, to the best of our knowledge. Although the bulk InAs1-yPy and In xGa1-xAs samples show good optical transmissions, PL transitions, and high carrier mobilities, they do exhibit some random compositional fluctuations across the sample. A practical method of extracting bandgap energies directly from the FTIR transmission spectra has been presented in this work, and the results are promising even though further refinement is required. Bandgap energies estimated from the transmission spectra agree well with those obtained from PL spectra and the previously reported values from the thin film studies. Overall, the optical and electrical properties of these crystals are well suited for a variety of device applications that do not require single crystalline material.

Wei, Jean

55

Molecular-beam epitaxial growth and characterization of indium-gallium-nitride based alloys, heterostructures and multi-quantum wells  

NASA Astrophysics Data System (ADS)

Optical devices based on III-V nitrides operating in the visible region involve GaN as well as InGaN alloys. The development of such devices requires the optimization of both GaN and InGaN alloys. This thesis addresses issues related to the growth and characterization of InGaN alloys, both in the form of thick films as well as in the form of double heterostructures (Al)GaN/InGaN/(Al)GaN or multi-quantum wells. Methods have been developed to grow pure GaN thin films with excellent structural and optoelectronic properties. Such films have been intentionally doped with Si (n-type) and Mg (p-type). The room temperature carrier concentrations in the n-type films can be controlled from 10sp{16}-10sp{19}\\ cmsp{-3} with peak mobilities of 200 cmsp2/V-sec. The p-type Mg-doped films were found to have carrier concentrations up to 5× 10sp{17} cmsp{-3} without the need for any post-growth processing for the activation of Mg-acceptors. The relation between XRD measurements and dislocation densities measured by TEM in these high quality films has also been determined. InGaN bulk films were found to undergo phase separation of pure InN as detected by XRD when the indium concentration exceeds 35%. However, such phase separation was not observed when the same alloys were incorporated in film thickness less than 500 A. By employing indium in thin InGaN layers in the form of double heterostructures (DH), up to 81% of indium has been successfully incorporated. Calculations indicate that this phase separation is thermodynamically expected since the growth temperature is within the miscibility gap. The critical temperature of miscibility for this pseudo-binary system, based on the delta lattice parameter theory, is computed to be 2457 K. Multi-quantum wells of InGaN/AlGaN with thickness of about 100 A for the wells and barriers were fabricated. Upon optical pumping at room temperature, such structures were found to emit narrow luminescence with tunable wavelength in the visible region and quantum efficiency significantly higher than bulk InGaN. Sub-micron spatial resolution photoluminescence studies revealed that radiative recombination efficiency in InGaN quantum wells is 50-60 times that in bulk GaN. Single quantum well/double heterostructure and multi-quantum well InGaN/(Al)GaN LED structures have been fabricated and evaluated. Typical DH LEDs had a turn-on voltage of about 2V. Optical spectra were characteristic of emission in the InGaN layer with FWHM of about 50 nm at room temperature. Issues related to the processing of these LED devices have also been addressed.

Singh, Rajminder

56

Gallium poisoning: a rare case report.  

PubMed

The authors present a case of a college student who suffered acute gallium poisoning as a result of accidental exposure to gallium halide complexes. This is extremely rare and has never been reported in the literature. Acute symptoms after the incident, which initially presented as dermatitis and appeared relatively not life-threatening, rapidly progressed to dangerous episodes of tachycardia, tremors, dyspnea, vertigo, and unexpected black-outs. Had there been effective emergency medical care protocols, diagnostic testing, treatment and antidotes, the latent manifestations of irreversible cardiomyopathy may have been prevented. Given how quickly exposure led to morbidity, this article aims to raise an awareness of the toxic potential of gallium. This has particular relevance for workers involved in the production of semiconductors where there is a potential for accidental exposure to gallium by-products during device processing. It may also have implications for dentists who use gallium alloys to replace mercury containing amalgam. In the absence of threshold limit values and exposure limits for humans, as well as emergency medical guidelines for treatment of poisoning, the case calls on the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration to establish guidelines and medical management protocols specific for gallium. PMID:22024274

Ivanoff, Chris S; Ivanoff, Athena E; Hottel, Timothy L

2012-02-01

57

Strained gallium nitride nanowires  

Microsoft Academic Search

Gallium nitride nanowires were synthesized on silicon substrates by chemical vapor deposition using the reaction of gallium and gallium nitride mixture with ammonia. Iron nanoparticles were used as catalysts. The diameter of nanowires is uniform as 25 nm and the lengths are 20-40 mum. The nanowires have single crystalline wurtzite structure with a few stacking faults. A careful examination into

Hee Won Seo; Seung Yong Bae; Hyunik Yang; Kwang Soo Park; Sangsig Kim

2002-01-01

58

Orthodontic silver brazing alloys.  

PubMed

Orthodontic silver brazing alloys suffer from the presence of cadmium, excessive flow temperatures, and crevice corrosion on stainless steel. Seven alloys were examined. Two alloys contained cadmium. The lowest flow temperature observed was 629 degrees C for a cadmium alloy and 651 degrees C for two cadmium free alloys. Three alloys had corrosion resistance superior to the other solders. Addition of low melting temperature elements gallium and indium reduced flow temperature in some cases but produced brittleness in the brazing alloy. PMID:2576971

Brockhurst, P J; Pham, H L

1989-10-01

59

Gallium in cancer treatment.  

PubMed

The trivalent gallium cation is capable of inhibiting tumor growth, mainly because of its resemblance to ferric iron. It affects cellular acquisition of iron by binding to transferrin, and it interacts with the iron-dependent enzyme ribonucleotide reductase, resulting in reduced dNTP pools and inhibition of DNA synthesis. The abundance of transferrin receptors and the up-regulation of ribonucleotide reductase render tumor cells susceptible to the cytotoxicity of gallium. Remarkable clinical activity in lymphomas and bladder cancer has been documented in clinical studies employing intravenous gallium nitrate, which is currently being re-evaluated in non-Hodgkin's lymphoma. An improved therapeutic index is expected to result from prolonged exposure to low steady-state plasma gallium levels. Attempts to accomplish this by oral administration of gallium chloride failed because of insufficient intestinal absorption. Complexation of gallium with ligands, which stabilize gallium against hydrolysis and facilitate membrane permeation, has been recognized as a promising strategy for overcoming these limitations. Two such gallium complexes, namely tris(3-hydroxy-2-methyl-4H-pyran-4-onato)gallium(III) (gallium maltolate) and tris(8-quinolinolato)gallium(III) (KP46), which both exhibit high bioavailability when administered via the oral route, are currently being evaluated in the clinical setting. PMID:15579097

Jakupec, Michael A; Keppler, Bernhard K

2004-01-01

60

Investigations in gallium removal  

SciTech Connect

Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated.

Philip, C.V.; Pitt, W.W. [Texas A and M Univ., College Station, TX (United States); Beard, C.A. [Amarillo National Resource Center for Plutonium, TX (United States)

1997-11-01

61

Gallium nitride optoelectronic devices  

NASA Technical Reports Server (NTRS)

The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

Chu, T. L.; Chu, S. S.

1972-01-01

62

Behavior of pure gallium in water and various saline solutions.  

PubMed

This study investigated the chemical stability of pure gallium in water and saline solutions in order to obtain fundamental knowledge about the corrosion mechanism of gallium-based alloys. A pure gallium plate (99.999%) was suspended in 50 mL of deionized water, 0.01%, 0.1% or 1% NaCl solution at 24 +/- 2 degrees C for 1, 7, or 28 days. The amounts of gallium released into the solutions were determined by atomic absorption spectrophotometry. The surfaces of the specimens were examined after immersion by x-ray diffractometry (XRD) and x-ray photoelectron spectroscopy (XPS). In the solutions containing 0.1% or more NaCl, the release of gallium ions into the solution was lowered when compared to deionized water after 28-day immersion. Gallium oxide monohydroxide was found by XRD on the specimens immersed in deionized water after 28-day immersion. XPS indicated the formation of gallium oxide/hydroxide on the specimens immersed in water or 0.01% NaCl solution. The chemical stability of pure solid gallium was strongly affected by the presence of Cl- ions in the aqueous solution. PMID:9555258

Horasawa, N; Nakajima, H; Takahashi, S; Okabe, T

1997-12-01

63

Zinc and gallium diffusion in gallium antimonide  

Microsoft Academic Search

Extrinsic diffusion of zinc (Zn) in gallium antimonide (GaSb) under Ga-rich conditions was analyzed on the basis of the kick-out and the dissociative diffusion mechanism. Accurate modeling of the experimental profiles by means of continuum theoretical calculations reveals that Zn diffusion proceeds via singly positively charged Zn interstitials (Zni+) . The changeover of Zni+ to substitutional gallium (Ga) sites, thereby

Kirsten Sunder; Hartmut Bracht; Samuel P. Nicols; Eugene E. Haller

2007-01-01

64

Optical Properties and Electronic Structures of d- and F-Electron Metals and Alloys, Silver-Indium Nickel - GOLD-GALLIUM(2), PLATINUM-GALLIUM(2), - - Cobalt-Aluminum CERIUM-TIN(3), and LANTHANUM-TIN(3)  

Microsoft Academic Search

Optical properties and electronic structures of disordered Ag_{1-x}In_ {x} (x = 0.0, 0.04, 0.08, 0.12) and Ni_{1-x}Cu_{x }(x = 0.0, 0.1, 0.3, 0.4) alloys and ordered AuGa_2, PtGa _2, beta^' -NiAl, beta^' -CoAl, CeSn_3, and LaSn_3 have been studied. The complex dielectric functions have been determined for Ag_{1-x}In _{x},Ni_{1-x}Cu_ {x},AuGa_2, and PtGa_2 in the 1.2-5.5 eV region and for CeSn_3

Kwang Joo Kim

1990-01-01

65

Gallium nitride and related materials  

SciTech Connect

The first International Symposium on Gallium Nitride and related materials was held on November 27--December 1, 1995, in Boston, Massachusetts, US. The symposium reflected the large amount of work that has taken place since the field exploded about two years ago with the announcement of commercial blue light emitting devices. The topics covered crystal growth, molecular beam growth techniques, chemical vapor deposition, alloys and novel growth techniques, structural properties, electronic properties, optical properties, point defects, hydrogen, etching and other material processes, surfaces and metal contacts, and devices. These proceedings represent the current state of understanding in the field, reflecting about 75 percent of the work presented at the symposium. One hundred and twenty eight papers have been processed separately for inclusion on the data base.

Ponce, F.A. [ed.] [Xerox Palo Alto Research Center, CA (United States); Dupuis, R.D. [ed.] [Univ. of Texas, Austin, TX (United States); Nakamura, S. [ed.] [Nichia Chemical Industries, Tokushima (Japan); Edmond, J.A. [ed.] [Cree Research, Inc., Durham, NC (United States)

1996-11-01

66

Gallium Arsenide Data Sheets.  

National Technical Information Service (NTIS)

These data sheets present a compilation of a wide range of electrical, optical and energy values for pure and variously-doped gallium arsenide in bulk and film form. Electrical properties include conductivity, resistivity, dielectric constant, Hall coeffi...

M. Neuberger

1965-01-01

67

Interactions of Zircaloy Cladding with Gallium: Final Report  

SciTech Connect

The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fhel, on cladding material performance. Three previous repmts"3 identified several compatibility issues relating to the presence of gallium in MOX fuel and its possible reaction with fiel cladding. Gallium initially present in weapons-grade (WG) plutonium is largely removed during processing to produce MOX fhel. After blending the plutonium with uranium, only 1 to 10 ppm gallium is expected in the sintered MOX fuel. Gallium present as gallium oxide (G~OJ could be evolved as the suboxide (G~O). Migration of the evolved G~O and diffusion of gallium in the MOX matrix along thermal gradients could lead to locally higher concentrations of G~03. Thus, while an extremely low concentration of gallium in MOX fiel almost ensures a lack of significant interaction of gallium whh Zircaloy fhel cladding, there remains a small probability that corrosion effects will not be negligible. General corrosion in the form of surface alloying resulting from formation of intermetallic compounds between Zircaloy and gallium should be ma& limited and, therefore, superficial because of the expected low ratio of gallium to the surface area or volume of the Zircaloy cladding. Although the expected concentration of gallium is low and there is very limited volubility of gallium in zirconium, especially at temperatures below 700 "C,4 grain boundary penetration and liquid metal embrittlement (LME) are forms of localized corrosion that were also considered. One fuel system darnage mechanism, pellet clad interaction, has led to some failure of the Zircaloy cladding in light-water reactors (LWRS). This has been attributed to stresses in the cladding and one or more aggressive fission products. Stress corrosion cracking by iodines' 6 and LME by cadmium7>8 have been reported, and it is known that Zircaloy can be embrittled by some low-melting metals, (e.g., mercury).g LME is a form of environmentally induced embrittlement that can induce cracking or loss of ductility. LME requties wetting and a tensile stress, but it does not require corrosion penetration. Experimentally, it has been demonstrated that gallium can cause embrittlement of some alloys (e.g., aluminum) at low temperatures,'"' ] ] but experiments relative to LME of zirconium by gallium have been limited and inconclusive.*2 This report describes a series of tests designed to establish the effects of low levels of residual gallium in WG-MOX fhel on its compatibility with Zircaloy. In addition, to establish damage mechanisms it was important to understand types of cladding interactions and available stiety margins with respect to gallium concentration.

D.F. Wilson; E.T. Manneschmidt; J.F. King; J.P. Strizak; J.R. DiStefano

1998-09-01

68

Visible light electroluminescent diodes of indium-gallium phosphide  

NASA Technical Reports Server (NTRS)

Vapor deposition and acceptor impurity diffusion techniques are used to prepare indium-gallium phosphide junctions. Certain problems in preparation are overcome by altering gas flow conditions and by increasing the concentration of phosphine in the gas. A general formula is given for the alloy's composition.

Clough, R.; Richman, D.; Tietjen, J.

1970-01-01

69

Amphoteric Impurities in Gallium Arsenide.  

National Technical Information Service (NTIS)

Gallium arsenide is already an important material for application in high frequency, low noise field effect transitors (FETs) and in optoelectronic devices, and future Gallium Arsenide (GaAs) high speed integrated circuits are expected to have a major imp...

G. E. Stillman

1987-01-01

70

Gallium Phosphide and the Gallium Arsenide-Gallium Phosphide System, Data Sheets.  

National Technical Information Service (NTIS)

These data sheets present a compilation of a wide range of electrical, optical and energy values for gallium phosphide and the gallium arsenidegallium phosphide system in bulk and film form. Electrical properties include lifetime and thermoelectric effect...

M. Neuberger

1965-01-01

71

Transport properties of proton-irradiated gallium nitride-based two-dimensional electron-gas system  

Microsoft Academic Search

A two-dimensional electron gas system (2DEG) is formed at the interface when a ternary alloy of aluminum gallium nitride is grown on gallium nitride. Very high carrier density can be achieved in these systems due to the strong piezoelectric and pyroelectric properties of the nitrides. The device was grown by molecular beam epitaxy and magnetron sputtering epitaxy. Through resistivity and

François Gaudreau; Patrick Fournier; Cosmo Carlone; Shyam M. Khanna; Haipeng Tang; Jim Webb; Alain Houdayer

2002-01-01

72

Aluminum battery alloys  

SciTech Connect

Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, D.S.; Scott, D.H.

1985-11-19

73

Aluminum battery alloys  

DOEpatents

Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, David S. (Richmond, VA); Scott, Darwin H. (Mechanicsville, VA)

1985-01-01

74

On the chemistry of gallium  

Microsoft Academic Search

The gallium subhalides Ga2Cl4·2dioxane and sonochemically prepared GaI were reacted with the carbonyl ferrate K[Cp(CO)2Fe] and the iron carbonyl dimer [Cp(CO)2Fe]2, respectively. In all the reactions performed, the gallium(I) and gallium(II) compounds disproportionated into elemental gallium and gallium(III) compounds. Several novel complexes containing Ga–FeCp(CO)2 fragments were isolated and characterized spectroscopically and by X-ray crystal structure analysis. These are compounds of

Gerald Linti; Guangming Li; Heinz Pritzkow

2001-01-01

75

Zinc and gallium diffusion in gallium antimonide  

NASA Astrophysics Data System (ADS)

Extrinsic diffusion of zinc (Zn) in gallium antimonide (GaSb) under Ga-rich conditions was analyzed on the basis of the kick-out and the dissociative diffusion mechanism. Accurate modeling of the experimental profiles by means of continuum theoretical calculations reveals that Zn diffusion proceeds via singly positively charged Zn interstitials (Zni+) . The changeover of Zni+ to substitutional gallium (Ga) sites, thereby forming the acceptor dopant ZnGa- , is concluded to be mainly mediated by neutral IGa0 and singly positively charged Ga interstitials IGa+ via the kick-out mechanism. Fitting of the Zn profiles provides the reduced Zni+ -mediated Zn diffusion coefficient and the relative contributions of IGa0 and IGa+ to Ga diffusion. These contributions to Ga diffusion are lower than the directly measured Ga diffusion coefficient, which indicates that Ga diffusion in GaSb is rather mediated by Ga vacancies than by Ga interstitials even under Ga-rich conditions. This finding supports the transformation reaction between native point defects in GaSb that was previously proposed to explain the Ga-vacancy-mediated diffusion of Ga in GaSb under Ga-rich conditions [H. Bracht Nature (London) 408, 69 (2000)].

Sunder, Kirsten; Bracht, Hartmut; Nicols, Samuel P.; Haller, Eugene E.

2007-06-01

76

Thermal Conductivity of Indium–Graphene and Indium-Gallium–Graphene Composites  

Microsoft Academic Search

Samples of graphene composites with a matrix of indium or indium-gallium alloy were prepared in the form of foils using exfoliated\\u000a graphene dispersions. The thermal conductivity of the composite samples with different thicknesses was determined using the\\u000a three-omega method. Indium–graphene composite samples with a thickness of 430 ?m exhibited a twofold increase in thermal conductivity, whereas indium-gallium–graphene composite samples with a

K. Jagannadham

2011-01-01

77

Gallium-containing anticancer compounds  

PubMed Central

There is an ever pressing need to develop new drugs for the treatment of cancer. Gallium nitrate, a group IIIa metal salt, inhibits the proliferation of tumor cells in vitro and in vivo and has shown activity against non-Hodgkin’s lymphoma and bladder cancer in clinical trials. Gallium can function as an iron mimetic and perturb iron-dependent proliferation and other iron-related processes in tumor cells. Gallium nitrate lacks cross resistance with conventional chemotherapeutic drugs and is not myelosuppressive; it can be used when other drugs have failed or when the blood count is low. Given the therapeutic potential of gallium, newer generations of gallium compounds are now in various phases of preclinical and clinical development. These compounds hold the promise of greater anti-tumor activity against a broader spectrum of cancers. The development of gallium compounds for cancer treatment and their mechanisms of action will be discussed.

Chitambar, Christopher R

2013-01-01

78

Compatibility of ITER candidate materials with static gallium  

SciTech Connect

Corrosion tests have been conducted to determine the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor (ITER) first wall/blanket systems, e.g., Type 316 stainless steel (SS), Inconel 625, and Nb-5 Mo-1 Zr. The results indicate that Type 316 SS is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400 C, corrosion rates for Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy are {approx} 4.0, 0.5, and 0.03 mm/yr, respectively. Iron, nickel, and chromium react rapidly with gallium. Iron shows greater corrosion than nickel at 400 C ({ge} 88 and 18 mm/yr, respectively). The present study indicates that at temperatures up to 400 C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The growth of intermetallic compounds may control the overall rate of corrosion.

Luebbers, P.R.; Chopra, O.K. [Argonne National Lab., IL (United States). Energy Technology Div.

1995-09-01

79

Gallium interactions with Zircaloy  

SciTech Connect

This study focuses on the effects of gallium ion implantation into zircaloy cladding material to investigate the effects that gallium may have in a reactor. High fluence ion implantation of Ga ions was conducted on heated Zircaloy-4 in the range of 10{sup 16}--10{sup 18} Ga ions/cm2. Surface effects were studied using SEM and electron microprobe analysis. The depth profile of Ga in the Zircaloy was characterized with Rutherford backscattering and SIMS techniques. Results indicate that the Zirc-4 is little affected up to a fluence of 10{sup 17} Ga ions/cm{sup 2}. After implantation of 10{sup 18} Ga ions/cm{sup 2}, sub-grain features on the order of 2 {micro}m were observed which may be due to intermetallic compound formation between Ga and Zr. For the highest fluence implant, Ga content in the Zirc-4 reached a saturation value of between 30 and 40 atomic %; significant enhanced diffusion was observed but gallium was not seen to concentrate at grain boundaries.

Woods, A.L. [ed.; West, M.K. [Texas A and M Univ., College Station, TX (United States). Dept. of Nuclear Engineering

1999-01-01

80

Fabrication of Aluminum Gallium Nitride/Gallium Nitride MESFET And It's Applications in Biosensing  

NASA Astrophysics Data System (ADS)

Gallium Nitride has been researched extensively for the past three decades for its application in Light Emitting Diodes (LED's), power devices and UV photodetectors. With the recent developments in crystal growth technology and the ability to control the doping there has been an increased interest in heterostructures formed between Gallium nitride and it's alloy Aluminium Gallium Nitride. These heterostructures due to the combined effect of spontaneous and piezoelectric effect can form a high density and a high mobility electron gas channel without any intentional doping. This high density electron gas makes these heterostructures ideal to be used as sensors. Gallium Nitride is also chemically very stable. Detection of biomolecules in a fast and reliable manner is very important in the areas of food safety and medical research. For biomolecular detection it is paramount to have a robust binding of the probes on the sensor surface. Therefore, in this dissertation, the fabrication and application of the AlGaN/GaN heterostructures as biological sensors for the detection of DNA and Organophosphate hydrolase enzyme is discussed. In order to use these AlGaN/GaN heterostructures as biological sensors capable of working in a liquid environment photodefinable polydimethyl-siloxane is used as an encapsulant. The immobilization conditions for a robust binding of thiolated DNA and the catalytic receptor enzyme organophosphate hydrolase on gold surfaces is developed with the help of X-ray photoelectron spectroscopy. DNA and OPH are detected by measuring the change in the drain current of the device as a function of time.

Alur, Siddharth

81

Methods of Fabricating Gallium Nitride Semiconductor Layers on Substrates Including Non-Gallium Nitride Posts, and Gallium Nitride Semiconductor Structures Fabricated Thereby.  

National Technical Information Service (NTIS)

A substrate includes non-gallium nitride posts that define trenches therebetween, wherein the non-gallium nitride posts include non-gallium nitride sidewalls and non-gallium nitride tops and the trenches include non-gallium floors. Gallium nitride is grow...

K. J. Linthicum R. F. Davis T. Gehrke

2005-01-01

82

Sputtering of tin and gallium-tin clusters  

SciTech Connect

Tin and gallium-tin clusters have been produced by 4 keV Ar{sup +} ion bombardment of polycrystalline tin and the gallium-tin eutectic alloy and analyzed by time-of-flight mass spectrometry. The sputtered neutral species were photoionized with 193 nm (6.4 eV) excimer laser light. Neutral tin clusters containing up to 10 atoms and mixed gallium-tin clusters Ga{sub (n-m)}Sn{sub m} with n {<=} 4 for the neutrals and N {<=} 3 for the sputtered ionic species have been detected. Laser power density dependent intensity measurements, relative yields, and kinetic energy distributions have been measured. The abundance distributions of the mixed clusters have been found to be nonstatistical due to significant differences in the ionization efficiencies for clusters with equal nuclearity but different number of tin atoms. The results indicate that Ga{sub 2}Sn and Ga{sub 3}Sn like the all-gallium clusters have ionization potentials below 6.4 eV. In the case of Sn{sub 5}, Sn{sub 6}, GaSn and Ga{sub (n-m)}Sn{sub m} clusters with n=2 to 4 and m>1, the authors detect species that have sufficient internal energy to be one photon ionized despite ionization potentials that are higher 6.4 eV. The tin atom signal that is detected can be attributed to photofragmentation of dimers for both sputtering from polycrystalline tin and from the gallium-tin eutectic alloy.

Lill, T.; Calaway, W.F.; Ma, Z.; Pellin, M.J.

1994-08-01

83

Superconducting Gallium Antimonide.  

PubMed

A metallic phase of gallium antimonide, obtained by quenching at approximately 120 kilobars to 77 degrees K and then releasing pressure, is a superconductor. The transition temperature depends on the annealing conditions; for samples annealed at 250 degrees C under pressure before quenching, it is 4.24 degrees +/- 0.10 degrees K, and H(c2) (the critical field) equals 2640 gauss at 3.50 degrees K. This temperature is higher than the 2.1 degrees K reported for metallic indium antimonide. PMID:17776623

McWhan, D B; Hull, G W; McDonald, T R; Gregory, E

1965-03-19

84

Gallium phosphide energy converters  

NASA Technical Reports Server (NTRS)

Betavoltaic power supplies based on gallium phosphide can supply long term low-level power with high reliability. Results are presented for GaP devices powered by Ni-63 and tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/cm(exp 2) have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. A small demonstration system has been assembled that generates and stores enough electricity to light up an LED.

Sims, P. E.; DiNetta, Louis C.; DuganCavanagh, K.; Goetz, M. A.

1996-01-01

85

Alloy  

NASA Astrophysics Data System (ADS)

The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by ?-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 ?m in the extruded ingot, down to 1.6 ?m for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

2014-07-01

86

alloys  

NASA Astrophysics Data System (ADS)

Structural, magnetic and magnetostrictive properties of Tb0.4Nd0.6(Fe0.8Co0.2) x (1.50 ? x ? 1.90) alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain technique. XRD analysis shows the presence of single Laves phase with a cubic MgCu2-type structure for the high Nd content alloy around the composition of x = 1.80, which tends to be formed by curing at relatively low annealing temperature. The easy direction of magnetization at room temperature is observed toward <111> axis, accompanied by a rhombohedral distortion with a large spontaneous magnetostriction ?111. An optimized effect on the linear anisotropic magnetostriction, 360 ppm at 3 kOe, was observed for the high Nd content Tb0.4Nd0.6(Fe0.8Co0.2)1.80 alloy, which can be attributed to its single Laves phase, the large ?111 (~1,520 ppm) of the MgCu2-type (Tb,Nd)(Fe,Co)2 phase and the good soft magnetic behaviors.

Pan, Z. B.; Liu, J. J.; Wang, R.; Liu, X. Y.; Wang, J.; Sun, N. K.; Si, P. Z.

2014-06-01

87

Mechanism of Hydrogen Generation via Water Reaction with Aluminum Alloys  

Microsoft Academic Search

Solid alloys of aluminum, gallium, indium and tin have been shown to react with water at room temperature to produce hydrogen and aluminum hydroxide in an exothermic reaction. The gallium, indium and tin components are inert and recoverable. The aluminum hydroxide can be recycled back to aluminum by the Hall-Heroult process. Several different experiments have been conducted to understand the

Go Choi; Jeffrey T. Ziebarth; Jerry M. Woodall; R. Kramer; D. Sherman; C. R. Allen

2010-01-01

88

Growth of Dislocation-Free Gallium Crystals.  

National Technical Information Service (NTIS)

Single crystals of gallium were grown with large portions free of dislocations detectable by anomalous transmission of x-rays. The crystals are grown by an unconstrained solidification technique. The very small supersaturation of vacancies in gallium at r...

S. H. McFarlane C. Elbaum

1965-01-01

89

Potential effects of gallium on cladding materials.  

National Technical Information Service (NTIS)

This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding ...

D. F. Wilson E. C. Beahm T. M. Besmann J. H. DeVan J. R. DiStefano

1997-01-01

90

NIST Realization of the Gallium Triple Point.  

National Technical Information Service (NTIS)

The gallium triple point (302.9166 K) instead of the gallium melting point (302.9146 K) is used at NIST in the realization of the International Temperature Scale of 1990 (ITS-90). Four different sources of gallium with purities of at least 99.999 995 wt. ...

G. F. Strouse

2008-01-01

91

Alloys  

NASA Astrophysics Data System (ADS)

The effects of mechanical deformation and subsequent annealing on the thermoelectric properties and microstructure have been investigated for p-type (Bi0.25Sb0.75)2Te3 alloys prepared by melting followed by quenching. The mechanically deformed pellets were prepared by repetition of cold-pressing of quenched samples at room temperature. Cold-pressed pellets were then annealed at 300°C in vacuum, and the thermoelectric properties and microstructure were traced through the course of the heat treatment. For the heavily deformed samples, the Seebeck coefficient rapidly increased at the very early stage of annealing and did not change as the annealing time increased, due to recrystallization of a new ?-phase which equilibrated at the annealing temperature of 300°C (?300-phase). At the initial stage of annealing (recovery stage), the electrical resistivity sharply increased, probably due to the interaction of antistructural defects with vacancies produced during the cold-pressing treatment. However, for the lightly deformed samples, recrystallization occurred only at some portion of the grain boundaries, and the newly generated ?300-phase slowly replaced the original, as-solidified ?ingot-phase.

Jung, Sung-Jin; Kim, Seong Keun; Park, Hyung-Ho; Hyun, Dow-Bin; Baek, Seung-Hyub; Kim, Jin-Sang

2014-06-01

92

Thermal expansion of gallium nitride  

Microsoft Academic Search

Lattice constants of gallium nitride (wurzite structure) have been measured at temperatures 294 - 753 K. The measurements were performed by using x-ray diffractometry. Two kinds of samples were used: (1) bulk monocrystal grown at pressure of 15 kbar, (2) epitaxial layer grown on a sapphire substrate. The latter had a smaller lattice constant in a direction parallel to the

M. Leszczynski; T. Suski; H. Teisseyre; P. Perlin; I. Grzegory; J. Jun; S. Porowski; T. D. Moustakas

1994-01-01

93

P-type gallium nitride  

DOEpatents

Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

Rubin, Michael (Berkeley, CA); Newman, Nathan (Montara, CA); Fu, Tracy (Berkeley, CA); Ross, Jennifer (Pleasanton, CA); Chan, James (Berkeley, CA)

1997-01-01

94

P-type gallium nitride  

DOEpatents

Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

1997-08-12

95

Chrome doped gallium arsenide evaluation  

Microsoft Academic Search

We received, for free, two sets of Chrome doped Gallium Arsenide (GaAs:Cr) wafers, one from Cominco Electronic Materials, Inc., and the other from Furakawa Electric Co., for the purpose of evaluation as potential material for high speed photoconductive detectors. In return for the free material we promised to give the two manufacturers feed back on our evaluation of these wafers.

M. D. Pocha; J. D. Morse; W. F. Brazes

1987-01-01

96

Gallium scan in intracerebral sarcoidosis  

SciTech Connect

Sarcoidosis involving the nervous system probably occurs in about 4% of patients. The usefulness of brain scintigraphy in these cases has been suggested. In this case of cerebral sarcoid granuloma, gallium imaging demonstrated the lesion before treatment and showed disappearance of the lesion after corticosteroid treatment, which correlated with the patient's clinical improvement.

Makhija, M.C.; Anayiotos, C.P.

1981-07-01

97

Extraction and separation of gallium, indium and thallium with several carboxylic acids from chloride media.  

PubMed

A method is proposed for the extraction and individual separation of trivalent gallium, indium and thallium with sec-octylphenoxy acetic acid (CA-12), sec-nonylphenoxy acetic acid (CA-100) and naphthenic acid (NA) from chloride media. The distribution equilibria of gallium (III), indium (III), thallium (III) and thallium (I) between carboxylic acids (CA-12, CA-100 and NA) dissolved in kerosene and acidic aqueous chloride media has been investigated as a function of the concentration of extractants and the concentration of hydrogen ion in aqueous phase. A possible mechanism of the extraction is discussed. The method permits rapid and precise individual separation of gallium (III), indium (III) and thallium (III), and is applicable to the analysis of alloy samples. PMID:18968979

Zhang, Xiuying; Yin, Guoyin; Hu, Zhiguo

2003-04-10

98

40 CFR 721.10391 - Copper gallium indium selenide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Copper gallium indium selenide. 721.10391...Chemical Substances § 721.10391 Copper gallium indium selenide. (a) Chemical...The chemical substance identified as copper gallium indium selenide (PMN...

2013-07-01

99

Source of fecal gallium--clinical implications: concise communication. [Gallium67 kinetics in rats  

Microsoft Academic Search

Bowel preparation before gallium-67 scanning often conists of cathartics, enemas, and a liquid or low-residue diet. Since human bile has approximately one-third the gallium concentration of the liver, the diet is presumably designed to minimize biliary excretion of gallium into the gut. To determine the actual biliary contribution to fecal gallium, the bile ducts of 15 rats were ligated and

A. Taylor; N. Chafetz; J. Hollenbeck; W. Hooser

1978-01-01

100

Measurement of arsenic and gallium content of gallium arsenide semiconductor waste streams by ICP-MS  

Microsoft Academic Search

The chemistry of semiconductor wafer processing liquid waste, contaminated by heavy metals, was investigated to determine arsenic content. Arsenic and gallium concentrations were determined for waste slurries collected from gallium arsenide (GaAs) wafer processing at three industrial sources and compared to slurries prepared under laboratory conditions. The arsenic and gallium content of waste slurries was analyzed using inductively coupled plasma

Keith W. Torrance; Helen E. Keenan; Andrew S. Hursthouse; David Stirling

2010-01-01

101

Gallium-Arsenide Point-Contact Diodes  

Microsoft Academic Search

This paper describes some of the work on gallium-arsenide point-contact diodes which is currently in progress at the Bell Telephone Laboratories, Holmdel, N. J. Gallium arsenide, one of the Group III-V intermetallic compounds, possesses properties which tend to make it superior to either silicon or germanium for many high-frequency diode applications. By controlling the resistivity of the gallium arsenide and

W. M. Sharpless

1961-01-01

102

Epitaxial Deposition Of Germanium Doped With Gallium  

NASA Technical Reports Server (NTRS)

Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

Huffman, James E.

1994-01-01

103

Superconductivity and structure of gallium under nanoconfinement  

Microsoft Academic Search

Superconductivity and crystalline structure were studied for two nanocomposites consisting of gallium loaded porous glasses with different pore sizes. The superconducting transition temperatures were found to differ from those in known bulk gallium modifications. The transition temperatures 7.1 and 6.7 K were ascribed to two new confined gallium structures, iota- and kappa-Ga, observed by synchrotron radiation x-ray powder diffraction. The

E. V. Charnaya; Cheng Tien; Min Kai Lee; Yu A. Kumzerov

2009-01-01

104

Superconductivity and structure of gallium under nanoconfinement  

Microsoft Academic Search

Superconductivity and crystalline structure were studied for two nanocomposites consisting of gallium loaded porous glasses with different pore sizes. The superconducting transition temperatures were found to differ from those in known bulk gallium modifications. The transition temperatures 7.1 and 6.7 K were ascribed to two new confined gallium structures, ?- and ?-Ga, observed by synchrotron radiation x-ray powder diffraction. The

E V Charnaya; Cheng Tien; Min Kai Lee; Yu A Kumzerov

2009-01-01

105

Substrates for gallium nitride epitaxy  

Microsoft Academic Search

In this review, the structural, mechanical, thermal, and chemical properties of substrates used for gallium nitride (GaN) epitaxy are compiled, and the properties of GaN films deposited on these substrates are reviewed. Among semiconductors, GaN is unique; most of its applications uses thin GaN films deposited on foreign substrates (materials other than GaN); that is, heteroepitaxial thin films. As a

L. Liu; J. H. Edgar

2002-01-01

106

Ion Implantation in Gallium Arsenide  

Microsoft Academic Search

Ion implantation is a useful method to incorporate dopants into semiconductors. Understanding implantation processes is essential to the advancement of solid state technology. Because of its technical importance, gallium arsenide (GaAs) was chosen for this study. Hall effect, x-ray diffraction, and electrochemical capacitance-voltage (CV) profiling were used to study activation of silicon implants as functions of dose and annealing temperature

John Hamilton Madok

1993-01-01

107

Hepatocellular carcinoma detection by gallium scan and subsequent treatment by gallium maltolate: rationale and case study.  

PubMed

Gallium is antiproliferative to many types of cancer, due primarily to its ability to act as a non-functional mimic of ferric iron (Fe(3+)). Because Fe(3+) is needed for ribonucleotide reductase activity--and thus DNA synthesis--gallium can inhibit DNA production and cell division. Diagnostic gallium scans have shown that hepatocellular carcinoma (HCC) is commonly avid for gallium. Furthermore, in vitro studies have found that gallium nitrate, and particularly gallium maltolate (GaM), have dose-dependent antiproliferative activity against HCC cell lines. Rationale thus exists to use GaM, an orally active compound that has been well tolerated in Phase I clinical trials, to treat patients whose HCC is gallium-avid in a gallium scan. Because gallium absorbed from orally administered GaM is bound predominately to serum transferrin, which travels to all tissues in the body, GaM has the potential to treat even distant metastases. A patient with advanced HCC (20 × 10 cm primary tumor, ascites around liver and spleen, resistant to Nexavar(®) (sorafenib)), whose cancer was highly gallium-avid in a (67)Ga-scan, was treated with oral gallium maltolate at 1500 mg/day q.d. After four weeks of treatment, the patient had a large reduction in pain, with greatly increased mobility and quality of life, and significantly lowered serum bilirubin and inflammation-related liver enzymes. At eight weeks, CT scans showed apparent necrosis of the tumor. PMID:21554205

Bernstein, Lawrence R; van der Hoeven, Jacobus J M; Boer, Robbert O

2011-07-01

108

Gallium nitride growth using diethyl gallium chloride as an alternative gallium source  

NASA Astrophysics Data System (ADS)

Diethyl gallium chloride (DEGaCl) was employed as an alternative gallium precursor in the epitaxial growth of GaN for producing a hydride vapor-phase epitaxy (HVPE)-like growth chemistry in a metal-organic vapor-phase epitaxy (MOVPE) system. The standard 'two-step' GaN growth process was carried out using this Cl-containing precursor and compared to the conventional growth using trimethyl gallium (TMGa) source under identical reactor conditions. The growth rate during DEGaCl-based growth decreases with increasing temperature, indicating that the growth front may be close to local thermodynamic equilibrium. A direct comparison of materials properties associated with these precursors in various structural combinations of buffer and high-temperature GaN epilayers was performed. Improved material properties and a significant difference in the surface morphology were observed in the case of DEGaCl-based high-temperature growth, as determined by X-ray diffraction, capacitance-voltage, atomic force microscopy and photoluminescence measurements. We attributed the improved growth behavior to the 'nearer-to-equilibrium' growth front that could result from the presence of HCl-related etching reactions.

Zhang, L.; Gu, S. L.; Kuech, T. F.; Boleslawski, Marek P.

2000-05-01

109

Determination of gallium by adsorptive stripping voltammetry.  

PubMed

A procedure for the determination of gallium by differential pulse adsorptive stripping voltammetry (DPADSV), using different complexing agents (ammonium pyrrolidine dithiocarbamate (APDC), pyrocatechol violet (PCV) and diethyldithiocarbamate (DDTC)), has been optimized. The selection of the experimental conditions was made using experimental design methodology. Under these conditions, the calibration was made and the detection limit was determined for each gallium-ligand complex. A robust regression method was applied which allowed the elimination of anomalous points. The detection limit, with alpha=beta=0.05, for gallium-APDC complex was 5.0x10(-8)moldm(-3), for gallium-PCV complex was 9.9x10(-9)moldm(-3), and the lowest detection limit (1.3x10(-9)moldm(-3)) was obtained with DDTC. For this reason, DDTC was selected for the determination of the gallium concentration in a certificate sample and in a spiked tap water sample. The linear dynamic range for gallium-APDC complex was from 5.0x10(-8) to 2.7x10(-7)moldm(-3), for gallium-PCV complex was from 5.0x10(-9) to 4.8x10(-7)moldm(-3), and for gallium-DDTC complex was from 1.0x10(-9) to 2.1x10(-7)moldm(-3). PMID:18969318

González, M Jesús Gómez; Renedo, Olga Dom? Nguez; Lomillo, M Asunción Alonso; Mart? Nez, M Julia Arcos

2004-02-27

110

An unusual case of gallium scan mimicking a bone scan.  

PubMed

Gallium-67 localization is based on the fact that it binds to plasma proteins like transferrin and lactoferrin, which have iron-binding sites. Abnormal biodistribution of gallium-67 citrate can occur in iron-overload states. We report one such case of gallium scan mimicking a bone scan due to skeletal uptake of gallium. PMID:22616033

Puranik, Ameya; Luthra, Karuna; Lele, R D

2012-01-01

111

An Unusual Case of Gallium Scan Mimicking a Bone Scan  

PubMed Central

Gallium-67 localization is based on the fact that it binds to plasma proteins like transferrin and lactoferrin, which have iron-binding sites. Abnormal biodistribution of gallium-67 citrate can occur in iron-overload states. We report one such case of gallium scan mimicking a bone scan due to skeletal uptake of gallium.

Puranik, Ameya; Luthra, Karuna; Lele, R. D.

2012-01-01

112

Pilot installation of the gallium-germanium solar neutrino telescope  

Microsoft Academic Search

The advantages and disadvantages of using a metal gallium target in a gallium solar neutrino experiment are briefly reviewed, and a pilot gallium-germanium installation using 7 tons of gallium metal is described. In particular, attention is given to the chemical procedure, the counting system, and preliminary results of Ge-71 and Ge-69 yields from cosmic rays. Finally, the possibility of conducting

I. R. Barabanov; E. P. Veretenkin; V. N. Gavrin; S. N. Danshin; L. A. Eroshkina; G. T. Zatsepin; Y. I. Zakharov; S. A. Klimova; Y. B. Klimov; T. V. Knodel

1985-01-01

113

Gallium Electromagnetic (GEM) Thrustor Concept and Design  

NASA Technical Reports Server (NTRS)

We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given in Fig. 1. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagneticpump[l]. At a designated time, a pulsed discharge (approx.10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx.500 I), send-stage puke which provides the primary electromagnetic (j x B) acceleration.

Polzin, Kurt A.; Markusic, Thomas E.

2006-01-01

114

Processing to obtain high-purity gallium  

NASA Astrophysics Data System (ADS)

Gallium has become increasingly popular as a substrate material for electronic devices. Aside from ore, gallium can be obtained from such industrial sources as the Bayer process caustic liquor that is a byproduct of bauxite processing, flue dust removed from the fume-collection system in plants that produce aluminum by the electrolytic process, zinc refinery residues, gallium scrap materials, and coal fly ash. The purification process for gallium can start with solvent-extraction processes where the concentrations of impurities, especially metals, are reduced to the ppm range. This article describes how ultra-purification techniques can be employed to reduce the undesirable impurities to the low ppb range. The various procedures described give an idea as to the extent of work needed to obtain and prepare high-purity gallium for electronic application.

Bautista, Renato G.

2003-03-01

115

Electrospun Gallium Nitride Nanofibers (abstract)  

NASA Astrophysics Data System (ADS)

The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH3 flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

2009-04-01

116

Clinical applications of Gallium-68.  

PubMed

Gallium-68 is a positron-emitting radioisotope that is produced from a (68)Ge/(68)Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. (68)Ga-DOTATOC, (8)Ga-DOTATATE, (68)Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with (68)Ga over the past few years around the world, including within the United States. An estimated ?10,000 scans are being performed yearly in Europe at about 100 centers utilizing (68)Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied (68)Ga-labeled imaging agents used in nuclear medicine. PMID:23522791

Banerjee, Sangeeta Ray; Pomper, Martin G

2013-06-01

117

Clinical Applications of Gallium-68  

PubMed Central

Gallium-68 is a positron-emitting radioisotope that is produced from a 68Ge/68Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. 68Ga-DOTATOC, 8Ga-DOTATATE, 68Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with 68Ga over the past few years around the world, including within the United States. An estimated ~10,000 scans are being performed yearly in Europe at about 100 centers utilizing 68Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied 68Ga-labeled imaging agents used in nuclear medicine.

Banerjee, Sangeeta Ray; Pomper, Martin G.

2013-01-01

118

The Soviet American Gallium Experiment (SAGE)  

SciTech Connect

A radiochemical experiment using the reaction v/sub e/ = /sup 71/Ga + e/sup e/ to determine the integral flux of low-energy neutrinos from the sun is currently under preparation at the Baksan Neutrino Observatory in the USSR. Measurements are scheduled to commence by late 1988 using /approximately/30 tonnes of metallic gallium. With this amount of gallium it should be possible to obtain a fractional statistical accuracy of 12 to 15% after one year (assuming the standard solar model neutrino flux). While initial measurements are in progress, installation of the remaining 30 tonnes of gallium will proceed in order to perform the full 60 tonne experiment.

Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.P.; Avdeyev, A.V.; Belousko, Yu.I.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Gavrin, V.N.; Grigorjev, A.M.; Kalikhov, A.V.; Kireyev, S.M.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentsevah, S.A.; Mirnov, I.N.; Ejikbosverpdze, Sh.M.; Ostrinsky, A.V.; Petukhov, V.V.; Pikhulya, O.E.; Pshukov, A.M.; Revzin, N.Ye.; Shikhin, A.A.; Shilo, Yu.I.; Slyusareva, Ye.D.; Strepanyuk, M.V.; Tikhonov, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Yants, V.E.; Zakhorov, Yu.I.; Zatsepin, G.T.; Cleveland, B.C.; Bowles, T.J.; Elliott, S.R.; O'Brien, H.A.; Wark, D.L.; Wilkerson, J.F.; Cherry, M.L.; Kouzes, R.T.

1988-01-01

119

In vitro bio-functionality of gallium nitride sensors for radiation biophysics  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Gallium nitride based sensors show promising characteristics to monitor cellular parameters. Black-Right-Pointing-Pointer Cell growth experiments reveal excellent biocompatibiltiy of the host GaN material. Black-Right-Pointing-Pointer We present a biofunctionality assay using ionizing radiation. Black-Right-Pointing-Pointer DNA repair is utilized to evaluate material induced alterations in the cellular behavior. Black-Right-Pointing-Pointer GaN shows no bio-functional influence on the cellular environment. -- Abstract: There is an increasing interest in the integration of hybrid bio-semiconductor systems for the non-invasive evaluation of physiological parameters. High quality gallium nitride and its alloys show promising characteristics to monitor cellular parameters. Nevertheless, such applications not only request appropriate sensing capabilities but also the biocompatibility and especially the biofunctionality of materials. Here we show extensive biocompatibility studies of gallium nitride and, for the first time, a biofunctionality assay using ionizing radiation. Analytical sensor devices are used in medical settings, as well as for cell- and tissue engineering. Within these fields, semiconductor devices have increasingly been applied for online biosensing on a cellular and tissue level. Integration of advanced materials such as gallium nitride into these systems has the potential to increase the range of applicability for a multitude of test devices and greatly enhance sensitivity and functionality. However, for such applications it is necessary to optimize cell-surface interactions and to verify the biocompatibility of the semiconductor. In this work, we present studies of mouse fibroblast cell activity grown on gallium nitride surfaces after applying external noxa. Cell-semiconductor hybrids were irradiated with X-rays at air kerma doses up to 250 mGy and the DNA repair dynamics, cell proliferation, and cell growth dynamics of adherent cells were compared to control samples. The impact of ionizing radiation on DNA, along with the associated cellular repair mechanisms, is well characterized and serves as a reference tool for evaluation of substrate effects. The results indicate that gallium nitride does not require specific surface treatments to ensure biocompatibility and suggest that cell signaling is not affected by micro-environmental alterations arising from gallium nitride-cell interactions. The observation that gallium nitride provides no bio-functional influence on the cellular environment confirms that this material is well suited for future biosensing applications without the need for additional chemical surface modification.

Hofstetter, Markus [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany)] [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany); Howgate, John [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany)] [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany); Schmid, Martin [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany)] [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany); Schoell, Sebastian; Sachsenhauser, Matthias [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany)] [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany); Adiguezel, Denis [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany)] [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany); Stutzmann, Martin; Sharp, Ian D. [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany)] [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany); Thalhammer, Stefan, E-mail: stefan.thalhammer@helmholtz-muenchen.de [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany)] [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany)

2012-07-27

120

System for Bulk Growth of Gallium Nitride. Vapor Phase Epitaxy of Gallium Nitride by Gallium Arc Evaporation.  

National Technical Information Service (NTIS)

A vapor phase growth system intended for the growth of bulk gallium nitride crystals was investigated. Potential advantages of the growth technique are cheap source materials of high purity, no corrosive gasses, and low operating and equipment costs. Ga c...

S. J. Heikman U. K. Mishra

2005-01-01

121

Gallium-67 activity in bronchoalveolar lavage fluid in sarcoidosis  

SciTech Connect

Roentgenograms and gallium-67 scans and gallium-67 counts of BAL fluid samples, together with differential cell counts, have proved to be useful in assessing activity and lung involvement in sarcoidosis. In active pulmonary sarcoidosis gallium-67 scans are usually positive. Quantitation of gallium-67 uptake in lung scans, however, may be difficult. Because gallium-67 uptake and cell counts in BAL fluid may be correlated, we set out to investigate gallium-67 activity in BAL fluid recovered from patient of different groups. Sixteen patients with recently diagnosed and untreated sarcoidosis, nine patients with healthy lungs, and five patients with CFA were studied. Gallium-67 uptake of the lung, gallium-67 activity in the lavage fluid, SACE and LACE levels, and alpha 1-AT activity were measured. Significantly more gallium-67 activity was found in BAL fluid from sarcoidosis patients than in that from CFA patients (alpha = .001) or patients with healthy lungs (alpha = .001). Gallium-67 activity in BAL fluid could be well correlated with the number of lymphocytes in BAL fluid, but poorly with the number of macrophages. Subjects with increased levels of SACE or serum alpha 1-AT showed higher lavage gallium-67 activity than did normals, but no correlation could be established. High gallium-67 activity in lavage fluid may be correlated with acute sarcoidosis or physiological deterioration; low activity denotes change for the better. The results show that gallium-67 counts in BAL fluid reflects the intensity of gallium-67 uptake and thus of activity of pulmonary sarcoidosis.

Trauth, H.A.; Heimes, K.; Schubotz, R.; von Wichert, P.

1986-01-01

122

Growth and Characterization of Copper INDIUM(1-X) Gallium(x) SELENIUM(2) and Copper Indium SULFUR(2Y) SELENIUM(2-2Y) Semiconductor Alloys and Evaluation of Their Electrochemical Solar Cells in IODINE(3)ION/IODIDE-ELECTROLYTE  

NASA Astrophysics Data System (ADS)

Crystals of CuIn_{1-x}Ga_{x} Se_2 and CuInS_ {2y}Se_{ 2-2y} were grown from stochiometric melts, by the gradient freeze method for different values of x and y respectively. With few exceptions these crystals were of p-type conductivity. In order to obtain n-type material, crystal growth experiments were also performed using Se deficient melt compositions, hence creating Se vacancies and related defects which act as donors. In addition, zone levelling was performed on two of the CuGa _{x}In _{1-x}Se_2 alloys to obtain more homogeneous crystals than accessible by gradient freezing. The band gap shift for these alloy systems with composition was established by photo-reflectance studies. The following band gap vs composition relationships were found. eqalign{E_{g } (CuIn_{1-x}Ga_{x }Se_2)&= 1.028 + 0.65 X + 0.21 X (X-1)cr E_{g} (CuInS_{2y}Se_{2-2y })& = 1.028 + 0.51 Y + 0.14 Y (Y-1)cr}Typical values for the carrier concentration were in the range of 10 ^{16} - 10^{17} per cm^3 as determined by Hall effect measurements. Chemical analysis of these bulk crystals were performed using Inductively Coupled Plasma Spectroscopy (ICP). The results of this method were reproducible within +/-1%. X ray diffraction studies were used to establish a and c axis lattice parameters. Linear relationships were found for the composition dependence of the lattice parameters. Photoluminescense studies on these alloys indicate that for CuIn_{1-x}Ga _{x}Se _2, there exists a greater variety of defect states inside the band gap than for comparable CuInS _{2y}Se_ {2-2y}. Semiconductor electrodes for these alloys were made by using In-Hg as back contact. Three-electrode photoelectrochemical cells were utilized using the standard calomel reference electrode and C as counter electrode. n-type CuInS _{2y}Se_ {2-2y} and CuIn_ {1-x}Ga_{x}Se_2 were evaluated in I_sp{3}{-} /I^- electrolyte. I-V curves indicate significant improvement in the values of V _{o.c} and F.F from the reported values for comparable n-CuInSe_2 electrochemical cell in the same electrolyte. Two of the best cells from each system were evaluated under AM0 conditions. The conversion efficiencies were found to be 6.8% for CuIn_{.88}Ga _{.12}Se_2 and 8.62% for CuInS_{.365} Se_{1.635}. p -type CuInS_{.2}Se _{1.8} photocathodes were evaluated in V^{+2}/V^ {+3} (E_0 = -0.49 volts) and Cr^{+2} /Cr^{+3} (E _0 = -0.65 volts) redox electrolyte. An improvement in the I-V characteristic was observed upon using more negative values of the electrode potential by reducing the ratio of trivalent ions to divalent ions by reduction with Zn metal. The I-V characteristics of p -CuInS_{2y}Se _{2-2y} significantly improved, upon letting the semiconductor electrode immersed in the electrolyte for some time, suggesting favorable surface conditioning by either etching of the electrode in the electrolyte solution or formation of a passivating film on the semiconductor electrode surface.

Abid, Bader

1991-02-01

123

Development of Gallium Arsenide for Infrared Windows.  

National Technical Information Service (NTIS)

This report describes methods for preparing high quality infrared transmitting gallium arsenide. The work is broadly divided into categories describing doping studies, vertical pulling techniques, liquid encapsulation, growth methods, horizontal Bridgman ...

H. C. Hafner G. R. Cronin

1975-01-01

124

Metal organic vapor phase epitaxy growth mechanisms of gallium antimonide and compositional grading in pseudomorphic gallium arsenide antimonide films  

NASA Astrophysics Data System (ADS)

The metal-organic vapor-phase epitaxy (MOVPE) of GaSb was studied by measuring vertical and lateral growth rates for varying reactor temperatures and precursor mole fractions for the growth chemistries of trimethyl gallium (TMG)/trimethyl antimony (TMSb) and triethyl gallium (TEG)/TMSb. A Langmuir-Hinshelwood mechanism, consistent with experimental data, involving the surface reaction of monomethyl gallium (MMG) and monomethyl antimony (MMSb) was proposed for the TMG/TMSb case. For the TEG/TMSb case a similar mechanism involving the surface reaction of diethyl gallium (DEG) and Ga with MMSb was proposed which was consistent with the experimental data. The proposed mechanisms, kinetic rate data from literature, and reactor geometry and conditions were then incorporated into a finite element simulation to gain further insight into conditions at the growth surface. TMG/TMSb results showed that lateral growth rates are extremely sensitive to small changes in the precursor mole fractions and exhibit two temperature regimes; a low temperature regime where lateral growth is limited by decomposition of adsorbed MMG and a high temperature regime where lateral growth trends are ascribed to desorption of MMG. TMG/TMSb lateral growth results exhibit an absence of observable surface chemistry effects. TEG/TMSb lateral growth results indicate that [01¯1¯] surfaces have higher growth rates than [01¯1] surfaces, display trends similar to vertical growth for varying precursor mole fractions, and exhibit a single growth temperature regime where lateral growth behavior is attributed to desorption of DEG. Compositional grading in pseudomorphic GaAs1-ySb y films was studied by comparing measured and simulated x-ray diffraction spectra of GaAs/GaAs1-ySby superlattices grown using various gas switching sequences during interlayer growth pauses. Deposition of a precise Sb overlayer prior to antimonide growth, the subsequent removal of the Sb overlayer by means of desorption, or "chemical flashoff", prior to non-antimonide growth, and a combination of arsenic-for-antimony exchange and surface roughening upon exposure of an antimonide surface to arsine were found to be key phenomena affecting the grading in pseudomorphic GaAs1-ySby films. Lattice-latching, a thermodynamic effect whereby alloy compositions are pinned near lattice-matched values during epitaxial growth, caused pseudomorphic GaAs1-ySby to contain y ? 0.20 while thick, relaxed GaAs1-ySb y layers grown under identical conditions contain y ? 0.40.

Hawkins, Brian

125

Development of gallium arsenide solar cells  

NASA Technical Reports Server (NTRS)

The potential of ion implantation as a means of developing gallium arsenide solar cells with high efficiency performance was investigated. Computer calculations on gallium arsenide cell characteristics are presented to show the effects of surface recombination, junction space-charge recombination, and built-in fields produced by nonuniform doping of the surface region. The fabrication technology is summarized. Electrical and optical measurements on samples of solar cells are included.

1973-01-01

126

GALLIUM ARSENATE REMOVAL FROM WASTE WATERS  

Microsoft Academic Search

The aim of this paper is to study the loss of gallium (Ga) and arsenic (As) loss during the sedimentation of gallium arsenate (GaAsO4) from waste solutions of GaAs epitaxial production by chloride method. The solid wastes of this semiconductor manufacturing process are removed from technological equipment by dissolution in an acidic etching solution. In order to recover valuable Ga

S. Baranov; B. Cinic; J. Redwing; V. Stavila

2005-01-01

127

Thyroid uptake of gallium in Graves' disease.  

PubMed

A patient with hyperthyroid Graves' disease presented with ptosis, leading to a workup for myasthenia gravis. An enlarged thymus gland was noted on computed tomography. A scan with gallium-67 citrate showed prominent and diffuse thyroid gland activity as well as prominent lacrimal activity. This finding of thyroid uptake of gallium led to the correct diagnosis of Graves' disease. Such a finding has not been reported previously. The associated thymic, thyroid, and orbital findings in Graves' disease are discussed. PMID:3180616

Allard, J C; Lee, V W; Franklin, P

1988-09-01

128

Let there be light [gallium nitride LED  

Microsoft Academic Search

The incandescent light bulb rolled back the night around the start of the 20th century. The gallium nitride LED will light the way in the 21st. The development of the gallium nitride (GaN) LED, made it possible to get white light from a semiconductor. GaN LEDs are already quietly transforming specialized illumination, including architectural and stage lighting, indoor and outdoor

G. Zorpette

2002-01-01

129

Gallium Nitride Growth Using Diethylgallium Chloride as an Alternative Gallium Source.  

National Technical Information Service (NTIS)

Metal organic vapor phase epitaxy (MOVPE) of GaN has been carried out using diethyl gallium chloride (DEGaCl) and ammonia. The growth rate and efficiency of the DEGaCl-based growth decreases with increasing temperature when compared to trimethyl gallium (...

L. Zhang R. Zhang M. P. Bolelawski T. F. Kuech

1999-01-01

130

The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal  

NASA Astrophysics Data System (ADS)

Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH2). The heats of solution for PuHS and PuDS are determined from PCT data in the ranges 350-625°C for gallium alloyed Pu and 400-575°C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

Richmond, S.; Bridgewater, J. S.; Ward, J. W.; Allen, T. H.

2010-03-01

131

Structural features of solid gallium in microporous glass  

Microsoft Academic Search

An experimental Debye-Scherrer study of structural features of gallium in porous glass with pore diameter d=4 nm is reported. Gallium structures different from the known bulk modifications have been discovered.

I. G. Sorina; E. V. Charnaya; L. A. Smirnov; Yu. A. Kumzerov; C. Tien

1998-01-01

132

Directing substrate morphology via self-assembly: ligand-mediated scission of gallium-indium microspheres to the nanoscale.  

PubMed

We have developed a facile method for the construction of liquid-phase eutectic gallium-indium (EGaIn) alloy nanoparticles. Particle formation is directed by molecular self-assembly and assisted by sonication. As the bulk liquid alloy is ultrasonically dispersed, fast thiolate self-assembly at the EGaIn interface protects the material against oxidation. The choice of self-assembled monolayer ligand directs the ultimate size reduction in the material; strongly interacting molecules induce surface strain and assist particle cleavage to the nanoscale. Transmission electron microscopy images and diffraction analyses reveal that the nanoscale particles are in an amorphous or liquid phase, with no observed faceting. The particles exhibit strong absorption in the ultraviolet (?200 nm), consistent with the gallium surface plasmon resonance, but dependent on the nature of the particle ligand shell. PMID:22023557

Hohman, J Nathan; Kim, Moonhee; Wadsworth, Garrett A; Bednar, Heidi R; Jiang, Jun; LeThai, Mya A; Weiss, Paul S

2011-12-14

133

Superconducting niobium alloys  

SciTech Connect

This patent describes a method of making a niobium alloy having the general formula Nb/sub 3/M where M is selected from the group consisting of aluminum, gallium, indium, tin, geranium, silicon, and mixtures thereof. The method comprising reacting NbX/sub y/ with M in a solution comprising a liquid alkali metal, where X is halogen and y is the valence of the niobium and an inert solid salt that has a melting point between about 450{sup 0}C and about 600{sup 0}C in an amount sufficient to absorb the exothermic heat of the reaction.

Charles, R.G.

1989-09-12

134

Gallium Zeolites for Light Paraffin Aromatization  

SciTech Connect

The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

Price, G.L.; Dooley, K.M.

1999-02-10

135

Quantitative chemical analysis of nickel-chromium dental casting alloys.  

PubMed

Twenty-nine brands of dental casting nickel-chromium alloys made in Japan for small castings were analyzed by electron probe X-ray microanalyzer. Nickel-chromium alloys for metal-ceramic application were composed primarily of nickel, chromium, and molybdenum with the exception of one brand. Of the nickel-chromium alloys for inlay, crown, and bridgework applications, 11 of the 22 alloys were up to the standard of the Ministry of Welfare specifications. And additive metal elements of these alloys were molybdenum, iron, copper, manganese, aluminum, silicon, tin, indium, silver, titanium, and gallium. PMID:2134288

Nagayama, K; Kuroiwa, A; Ando, Y; Hashimoto, H

1990-01-01

136

Production of gallium atoms by excimer laser photolysis of trimethyl gallium  

SciTech Connect

The gas phase kinetics of group III elements such as gallium are important in possible chemically driven energy transfer lasers and in chemical vapor deposition processes in the electronics industry. Excimer laser photodissociation of volatile gallium compounds via multiple photon process provides, in principle, a convenient room temperature source of gallium atoms for study using laser photolysis-laser induced fluorescence techniques. In this paper, we report preliminary results of the multiple photon dissociation of trimethyl gallium at 193 nm. Prompt emission from a number of excited gallium states (5 /sup 2/S, 4 /sup 2/D, 6 /sup 2/S, 6 /sup 2/P/sup 0/, 5 /sup 2/D, and 4 /sup 4/P) has been observed. The time histories of the ground state (4/sup 2/P/sup 0//sub 1/2/) and the metastable (4 /sup 2/P/sup 0//sub 3/2/) have been measured using laser induced fluorescence. The resulting time profiles are complicated even in the absence of a reactant gas by the apparent production of ground state gallium at relatively long times (approx. 10 ..mu..s) after the excimer laser pulse. Possible mechanisms for this (i.e., radical reactions to produce gallium, energy transfer cascading from high lying metastable states, ionic processes, etc.) are being investigated. These results indicate that the photodissociation of trimethyl gallium at 193 nm is complex. Photolysis studies at other wavelengths and with other precursors are in progress to find a cleaner source of gas phase atomic gallium for kinetic studies. 20 refs., 7 figs.

Baughcum, S.L.; Oldenborg, R.C.; Winn, K.R.; Hof, D.E.

1985-03-01

137

Single gallium nitride nanowire lasers  

NASA Astrophysics Data System (ADS)

There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q ~ 103) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV ?J cm-2) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources.

Johnson, Justin C.; Choi, Heon-Jin; Knutsen, Kelly P.; Schaller, Richard D.; Yang, Peidong; Saykally, Richard J.

2002-10-01

138

Chrome doped gallium arsenide evaluation  

SciTech Connect

We received, for free, two sets of Chrome doped Gallium Arsenide (GaAs:Cr) wafers, one from Cominco Electronic Materials, Inc., and the other from Furakawa Electric Co., for the purpose of evaluation as potential material for high speed photoconductive detectors. In return for the free material we promised to give the two manufacturers feed back on our evaluation of these wafers. The primary purpose of this report is to present the results of our evaluation of these wafers and conclusions regarding the usefulness of heavily doped GaAs:Cr for photoconductive detectors. We have found that response times of less than 100 ps (FWHM) are possible with GaAs:Cr detectors, but that there are several time constants to the decay which result in very long ''tails'' to the impulse response of these detectors. These long tails are unacceptable for most detector applications, but there may be some special cases where GaAs:Cr could be used. 5 figs., 1 tab.

Pocha, M.D.; Morse, J.D.; Brazes, W.F.

1987-10-10

139

New SMU Gallium Fixed-Point Cells  

NASA Astrophysics Data System (ADS)

In the framework of the European research project EURAMET 732, the Slovak Institute of Metrology (SMU) built three primary gallium fixed-point cells of different designs. The cells are designed for the calibration of the long-stem SPRT. In regard to the procedure commonly used at SMU when realizing the gallium point, the cells are designed for use in a stirred liquid bath. This article provides information about the cell designs, materials used, method of filling, and results of the performed experiments. The experiments were focused on the study of the cells' metrological characteristics, some effects that could influence the melting-point temperature and the effect of the melted metal fraction on the immersion profile. New cells were compared with the SMU reference gallium cell.

Ranostaj, Juraj; ?uriš, Stanislav; Knorová, Renáta; Kaskötö, Mariana; Vysko?ilová, Irena

2011-08-01

140

/sup 67/Gallium lung scans in progressive systemic sclerosis  

SciTech Connect

/sup 67/Gallium lung scans were performed in 19 patients with progressive systemic sclerosis (scleroderma). Results were expressed quantitatively as the /sup 67/Gallium Uptake Index. The mean total pulmonary /sup 67/Gallium Uptake Index in patients was significantly higher than that in controls (41 versus 25), and 4 patients (21%) fell outside the normal range. There were no clinical or laboratory variables that correlated with the /sup 56/Gallium uptake. Increased pulmonary /sup 67/Gallium uptake in scleroderma may prove useful as an index of pulmonary disease activity.

Baron, M.; Feiglin, D.; Hyland, R.; Urowitz, M.B.; Shiff, B.

1983-08-01

141

Gallium nitride as a material for spintronics  

NASA Astrophysics Data System (ADS)

The literature on the magnetic properties of GaN doped with magnetic impurities: the transition metals (Mn, Cr, Fe, Ni, and V) and rare earth elements (Gd, Eu, and Sm), as well as gallium nitride containing high concentration of gallium vacancies and quantum dots is reviewed. The properties of GaN doped by ion implantation and during the MBE and MOVPE growth of layers are considered. The undoped GaN and GaN films doped with the transition metals and rare earth elements often retain ferromagnetic properties at room temperature.

Khludkov, S. S.; Prudaev, I. A.; ??lbanov, ?. P.

2013-01-01

142

Modeling of liquid encapsulated gallium melts  

NASA Astrophysics Data System (ADS)

Liquid encapsulation crystal growth from the melt plays an important role in space processing. Use of an encapsulant may avoid evaporation of volatile components and may control thermocapillary flow, which becomes important in microgravity. In the present work the fluid physics of encapsulated liquid gallium is studied analytically and numerically in preparation to forthcoming experiments. It is shown that flow in the viscous encapsulant is essentially negligible and that liquid encapsulation reduces flow velocities in the encapsulated electronic melt. Flow velocity in the gallium is the main parameter in the studies.

Campbell, T. A.; Koster, J. N.

1995-06-01

143

Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor.  

National Technical Information Service (NTIS)

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT's) are microwave power devices that have the performance characteristics to improve the capabilities of current and future Navy radar and communication systems. The Office of Naval Research (O...

K. L. Holmes

2002-01-01

144

Optical identification of the gallium vacancy in neutron-irradiated gallium arsenide  

Microsoft Academic Search

Gallium arsenide grown by the metallorganic-chemical-vapor-deposition method was irradiated at room temperature with fast neutrons in the fluence range 1012 to 3×1015 cm-2 (1.00 MeV equivalent fluence in gallium arsenide). The effects of neutron irradiation were studied by photoluminescence (PL) spectroscopy in the energy range 0.5-1.55 eV. In the samples irradiated to 3×1013 cm-2 and higher fluences, we observe a

Anouar Jorio; Aiguo Wang; Martin Parenteau; Cosmo Carlone; Nelson L. Rowell; Shyam M. Khanna

1994-01-01

145

Synchrotron X-Ray Fluorescence Microscopy of Gallium in Bladder Tissue following Gallium Maltolate Administration during Urinary Tract Infection  

PubMed Central

A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 ?g/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli.

Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L.; Blyth, Robert I. R.; Sham, Tsun-Kong; Dowling, Patricia M.; Thompson, Julie

2013-01-01

146

Gallium: Thermal Conductivity; Supercooling; Negative Pressure  

Microsoft Academic Search

The thermal conductivity of liquid gallium does not appear to have heretofore been measured. The method employed involved a comparison with the known thermal conductivity of mercury. The two liquids were sealed in two thin-walled glass tubes (30 cm long, 10 mm bore), the upper ends being inserted vertically through the bottom of a boiler containing boiling water. The tubes

Lyman J. Briggs

1957-01-01

147

Anisotropy of the magnetic susceptibility of gallium  

USGS Publications Warehouse

The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

Pankey, Jr. , T.

1960-01-01

148

Russian-American Gallium solar neutrino Experiment.  

National Technical Information Service (NTIS)

The Russian-American Gallium solar neutrino Experiment (SAGE) is described. The solar neutrino flux measured by 31 extractions through October, 1993 is presented. The result of 69 (+-) (10 to the -7th power) to the 5th power SNU is to be compared with a s...

S. R. Elliott J. N. Abdurashitov T. J. Bowles

1995-01-01

149

PSG masks for diffusions in gallium arsenide  

Microsoft Academic Search

This paper describes the use of phosphosilicate glass (PSG) films as an effective mask against zinc and tin diffusions in gallium arsenide. It is shown that films with a high phosphorus pentoxide content (as much as 30 percent by weight) can be used to obtain adequate crack-free masks against these dopants. Effective masking was obtained for diffusion depths (unmasked regions)

B. J. Baliga; S. K. Ghandhi

1972-01-01

150

Gallium Electromagnetic (GEM) Thruster Performance Measurements  

NASA Technical Reports Server (NTRS)

Discharge current, terminal voltage, and mass bit measurements are performed on a coaxial gallium electromagnetic thruster at discharge currents in the range of 7-23 kA. It is found that the mass bit varies quadratically with the discharge current which yields a constant exhaust velocity of 20 km/s. Increasing the electrode radius ratio of the thruster from to 2.6 to 3.4 increases the thruster efficiency from 21% to 30%. When operating with a central gallium anode, macroparticles are ejected at all energy levels tested. A central gallium cathode ejects macroparticles when the current density exceeds 3.7 10(exp 8) A/square m . A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma. The spectra show that neutral, singly, and doubly ionized gallium species are present in the discharge, as well as annular electrode species at higher energy levels. Axial Langmuir triple probe measurements yield electron temperatures in the range of 0.8-3.8 eV and electron densities in the range of 8 x 10(exp )20 to 1.6 x 10(exp 21) m(exp -3) . Triple probe measurements suggest an exhaust plume with a divergence angle of 9 , and a completely doubly ionized plasma at the ablating thruster cathode.

Thomas, Robert E.; Burton, Rodney L.; Polzin, K. A.

2009-01-01

151

Extrapulmonary localization of gallium in sarcoidosis  

SciTech Connect

This paper describes the spectrum of extrapulmonary localization of gallium in patients with sarcoidosis. The usefulness of Ga-67 scintiscans in detecting clinically occult lesions, in directing clinicians to accessible sites for biopsy, and in following the course of extrapulmonary sites of involvement with therapy is emphasized.

Rohatgi, P.K.; Singh, R.; Vieras, F.

1987-01-01

152

Superconductivity of gallium in various confined geometries  

Microsoft Academic Search

The superconductivity of gallium in porous glasses with various pore sizes and in opals is studied using a superconducting quantum interference device magnetometer. The single and double superconducting phase transitions are observed for different samples. Magnetization hysteresis loops are also measured and found to be dependent on pore sizes and geometry. The changes in magnetization below about 6.4 K are

E. V. Charnaya; C. Tien; K. J. Lin; C. S. Wur; Yu. A. Kumzerov

1998-01-01

153

SPECT gallium imaging in abdominal lymphoma  

SciTech Connect

A case of non-Hodgkin's lymphoma of the abdomen studied by gallium SPECT imaging is reported. The tomographic slices accurately demonstrated the location of residual disease after chemotherapy in the region of the transverse mesocolon. Previous transmission CT had shown considerable persistent retroperitoneal lymphadenopathy, but was not helpful in determining the presence of viable lymphoma.

Adcock, K.A.; Friefeld, G.D.; Waldron, J.A. Jr.

1986-05-01

154

Atomistic modeling of thermodynamic properties of Pu-Ga alloys based on the Invar mechanism  

NASA Astrophysics Data System (ADS)

We present an atomistic model that accounts for a range of anomalous thermodynamic properties of the fcc ? phase of Pu-Ga alloys in terms of the Invar mechanism. Two modified embedded atom method potentials are employed to represent competing electronic states in ?-Pu, each of which has an individual configuration dependence as well as distinct interactions with gallium. Using classical Monte Carlo simulations, we compute the temperature dependence of various thermodynamic properties for different dilute gallium concentrations. The model reproduces the observed effects of excessive volume reduction along with a rapid shift in thermal expansion from negative to positive values with increasing gallium concentration. It also predicts progressive stiffening upon dilute-gallium alloying, while the calculated thermal softening is nearly independent of the gallium concentration in agreement with resonant ultrasound spectroscopy measurements in the literature. Analysis of the local structure predicted by the model indicates that the distribution of the gallium atoms is not completely random in the ? phase due to the presence of short-range order associated with the Invar mechanism. This effect is consistent with the nanoscale heterogeneity in local gallium concentration which is observed in recent extended x-ray absorption fine structure spectroscopy experiments. Implications of the Invar effect for phase stability and physical interpretations of the two states are also discussed.

Lee, Tongsik; Taylor, Christopher D.; Lawson, A. C.; Conradson, Steven D.; Chen, Shao Ping; Caro, A.; Valone, Steven M.; Baskes, Michael I.

2014-05-01

155

Gallium 67 scintigraphy in glomerular disease  

SciTech Connect

To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

1988-12-01

156

40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.  

Code of Federal Regulations, 2010 CFR

...and Secondary Germanium and Gallium Subcategory § 421.180 ...and secondary germanium and gallium subcategory. The provisions...discharges resulting from the production of germanium or gallium from primary and secondary...

2009-07-01

157

40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.  

Code of Federal Regulations, 2010 CFR

...and Secondary Germanium and Gallium Subcategory § 421.180 ...and secondary germanium and gallium subcategory. The provisions...discharges resulting from the production of germanium or gallium from primary and secondary...

2010-07-01

158

Gallium nitride nanowire electromechanical resonators  

NASA Astrophysics Data System (ADS)

Nanoscale mechanical resonators are of great interest for high-resolution sensing applications, where the small resonator mass and high quality factor (Q, defined as resonance frequency f0 over full width at half maximum power) lead to unprecedented sensitivity. Here, we investigate gallium nitride (GaN) nanowire (NW) resonators. The single-crystal, c-axis NWs are 5 mum -- 20 mum long, with diameters from 50 nm -- 500 nm, and grow essentially free of defects. Our initial experiments involve measuring the resonances of as-grown NWs in a scanning electron microscope, where we observe exceptionally high Q values of 10 4 -- 105, one to two orders of magnitude higher than most NWs of comparable size. Using a single NW as a mass sensor, we then demonstrate a sub-attogram mass sensitivity. To provide a more flexible measurement technique that avoids electron-microscope detection, we fabricate doubly clamped NWs with an entirely electronic drive and readout scheme using a combination of lithographic patterning and dielectrophoresis. An electrostatic gate induces vibration, while readout utilizes the piezoresistivity of GaN. Observed resonances range from 9--36 MHz with Q values typically around 103 at room temperature and 10 -4 Pa. We use the behavior of f0 and Q to sense the NW's local environment, such as the additional sources of energy dissipation not present in the as-grown NWs. By cooling the device to 8 K, Q increases by an order of magnitude to above 104, with a highest value to date of 26,000 under vacuum. We explore additional NW properties through the thermal noise in the NW's mechanical motion and the exponential decay of mechanical motion in the presence of burst drive. Finally, we investigate the low-frequency 1/f parameter noise displayed by f0. We show that the noise in f0 is consistent with noise in the NW's resistance leading to temperature noise from local Joule heating, which in turn generates resonance frequency noise. For sensor applications, there will be optimal drive conditions that balance the f 0 noise with the signal-to-noise ratio of the system. With these insights, along with the simple drive and readout technique, these GaN-NW doubly clamped resonators have significant potential for high-resolution sensing applications.

Gray, Jason Michael

159

Ammonothermal Growth of Gallium Nitride  

NASA Astrophysics Data System (ADS)

Bulk, single crystal Gallium Nitride (GaN) crystals are essential for enabling high performance electronic and optoelectronic devices by providing arbitrarily oriented, high quality, large, single crystal GaN substrates. Methods of producing single crystals of sufficient size and quality at a rate that would enable successful commercialization has been a major focus for research groups and companies worldwide. Recent advances have demonstrated remarkable improvements, though high cost and lack of high volume production remain key challenges. Major investments in bulk GaN growth were made at UCSB with particular focus on the ammonothermal method. The existing lab was upgraded and a new facility was designed and built with improved experimental setups for ammonothermal growth of GaN. The facilities can simultaneously operate up to 15 reactors of differing designs and capabilities with the ability to grow crystals up to 2 inches in diameter. A novel in-situ technique was devised to investigate the growth chemistry which occurs at typical operating conditions of 3,000 atm and 600 °C. Improvements in ammonothermal GaN include improved growth rates for c-plane by a factor of four to 344 ?m/day with an overall record growth rate of 544 ?m/day achieved for the (112¯2) plane. Crystal qualities comparable to that of the seed crystal were achieved. Impurity concentrations for transition metals were consistently reduced by a factor of 100 to concentrations below 1017 atoms/cm3. Optical transparency was improved by significantly reducing the yellow coloration typically seen for ammonothermal GaN. Single crystal GaN was successfully grown on large seeds and a 1 inch x ½ inch x ½ inch GaN crystal was demonstrated. To better understand the growth chemistry, models were created for the decomposition of ammonia under growth conditions, with initial experiments performed using the designed in-situ setup to verify the model's accuracy. To investigate the surface morphology and stability of basic ammonothermal GaN, various off-oriented HVPE GaN seed crystals were grown on and analyzed for growth rate, crystal quality, impurity incorporation, optical absorption, and surface morphology. A natural tendency for m-plane to off-orient itself by 0.5-1.5° towards-c-plane was observed, along with a region of apparent surface stability ranging from m-plane to {101¯1¯}.

Pimputkar, Siddha

160

Ion Implantation in Gallium Arsenide  

NASA Astrophysics Data System (ADS)

Ion implantation is a useful method to incorporate dopants into semiconductors. Understanding implantation processes is essential to the advancement of solid state technology. Because of its technical importance, gallium arsenide (GaAs) was chosen for this study. Hall effect, x-ray diffraction, and electrochemical capacitance-voltage (CV) profiling were used to study activation of silicon implants as functions of dose and annealing temperature and time. The annealing of crystalline damage and activation of dopants proceeds in a definite sequence. Implantation damage is annealed at approximately 625^ circC, with activation taking place between 625 and 675^circC. The electron profiles arising from Si implantation into GaAs possess long tails. Increasing the annealing temperature to greater than 900^circC results in a shortening of the tail because of the formation of an unknown acceptor defect. This result is reproducible and was used to enhance the performance of GaAs JFETs. Co-implantation of In or Ga with C was investigated by Local Vibrational Mode Spectroscopy (LVM), Rutherford Backscattering (RBS), Particle-Induced X-Ray Emission (PIXE), Photoluminescence (PL), and Hall effect. The dose of the C was 5 times 10^ {14} cm^{-2} 27 keV, while the doses of In, 185 keV, or Ga, 160 keV, ranged from 5 times 10 ^{13} to 5 times 10^{15} cm ^{-2}. The data shows that 99% of the C, when implanted alone and annealed, is not located as isolated, substitutional atoms on either sublattice, but in non-substitutional, inactive sites. The co-implanted ion acts to increase both the concentration of C _{rm As} ((C_ {rm As})) and the sheet hole concentration. For co-implant doses of 5 times 10 ^{13} and 5 times 10^{14} cm ^{-2}, these values are in good agreement. A co-implant dose of 5 times 10^{15} cm ^{-2} results in a hole concentration that is 30% less than the (C_{rm As}) and the co-implanted ions begin to occupy non-substitutional sites. The reduction in the concentration of holes due to C_{rm As} appears to be caused by a compensating donor defect which limits the maximum sheet hole concentration obtainable by the co-implantation technique in GaAs.

Madok, John Hamilton

161

Inflammatory pseudotumor: A gallium-avid mobile mesenteric mass  

SciTech Connect

An 8-yr-old boy with a 1-mo history of culture-negative fever and anemia underwent gallium, ultrasound, and computed tomography studies as part of the evaluation of a fever of unknown origin. These studies revealed a mobile gallium-avid solid abdominal mass subsequently proven to be an inflammatory pseudotumor of the mesentery, a rare benign mass. This report documents the gallium-avid nature of this rare lesion and discusses associated characteristic clinical, pathologic, and radiographic features.

Auringer, S.T.; Scott, M.D.; Sumner, T.E. (Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC (USA))

1991-08-01

162

Interactions of Zircaloy cladding with gallium: 1998 midyear status  

SciTech Connect

A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge}300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

1998-06-01

163

Interactions of zircaloy cladding with gallium -- 1997 status  

SciTech Connect

A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance of prototypic Zircaloy cladding materials against: (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge} 300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

Wilson, D.F.; DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.

1997-11-01

164

Surface photovoltage spectroscopy applied to gallium arsenide surfaces  

NASA Technical Reports Server (NTRS)

The experimental and theoretical basis for surface photovoltage spectroscopy is outlined. Results of this technique applied to gallium arsenide surfaces, are reviewed and discussed. The results suggest that in gallium arsenide the surface voltage may be due to deep bulk impurity acceptor states that are pinned at the Fermi level at the surface. Establishment of the validity of this model will indicate the direction to proceed to increase the efficiency of gallium arsenide solar cells.

Bynik, C. E.

1975-01-01

165

The physics and modeling of gallium arsenide solar cells  

Microsoft Academic Search

Gallium arsenide is a versatile semiconductor used in many devices. Due to its nearly ideal bandgap energy for solar energy conversion and its compatibility with AlGaAs, gallium arsenide's use in solar cells has been widespread and is growing. Only its chief rival, silicon, is more popular as a high-efficiency material. To continue gallium arsenide's growth, this research was conducted for

Paul David DeMoulin

1988-01-01

166

Survey of the market, supply and availability of gallium  

SciTech Connect

The objective of this study was to assess the present consumption and supply of gallium, its potential availability in the satellite power system (SPS) implementation time frame, and commercial and new processing methods for increasing the production of gallium. Findings are reported in detail. The findings strongly suggest that with proper long range planning adequate gallium would be available from free-enterprise world supplies of bauxite for SPS implementation.

Rosi, F.D.

1980-07-01

167

Measurement of the solar neutrino capture rate with gallium metal  

Microsoft Academic Search

The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2+7.2+3.5-7.0-3.0 SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted standard solar model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting

J. N. Abdurashitov; V. N. Gavrin; S. V. Girin; V. V. Gorbachev; T. V. Ibragimova; A. V. Kalikhov; N. G. Khairnasov; T. V. Knodel; I. N. Mirmov; A. A. Shikhin; E. P. Veretenkin; V. M. Vermul; V. E. Yants; G. T. Zatsepin; T. J. Bowles; W. A. Teasdale; D. L. Wark; M. L. Cherry; J. S. Nico; B. T. Cleveland; R. Davis; K. Lande; P. S. Wildenhain; S. R. Elliott; J. F. Wilkerson

1999-01-01

168

New gallium precursors for the formation of high purity gallium arsenide by metal organic vapor phase deposition  

NASA Astrophysics Data System (ADS)

The reduction of gallium trichloride monoammonia adduct with lithium hydride affords lithium trichlorohydrido gallate whereas the non-coordinated trichloride affords the known species, lithium tetrahydrido gallate. Attempts to prepare the ammonia adduct of gallane via lithium tetrahydrido gallate and ammonium chloride resulted in decomposition with hydrogen evolution. Exploratory investigation geared towards the formation of gallium perfluoroalkyls, via discharge reactions involving hexafluoroethane and trifluoroiodomethane, resulted in the gallium reduction of the pyrex reactors - construction of quartz reactors is therefore necessitated.

Schram, E. P.

1984-06-01

169

Scanning probe microscopy on new dental alloys  

NASA Astrophysics Data System (ADS)

Surface analytical methods such as scanning force microscopy (SFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface properties of amalgam substitutes as tooth filling materials. In particular the corrosion and the passivation behavior of new gallium restorative materials were studied. To give relevant practical data, the measurements were performed with and without the alloys being stored in artificial saliva to simulate physiological oral conditions.

Reusch, B.; Geis-Gerstorfer, J.; Ziegler, C.

170

Gallium Scan in Diagnosing Ocular Sarcoidosis  

PubMed Central

A 40-year-old man presented with floaters and painless progressive blurring of vision in the right eye for one month duration. Visual acuity in the right eye was 6/24. There was mild anterior chamber reaction and vitritis. The optic disc was swollen and elevated with presence of granulomatous lesion in the optic disc head. Blood investigations were unremarkable. Serum angiotensin converting enzyme (ACE) was normal and conjunctival biopsy showed presence of inflammatory cells. B-Scan ultrasound revealed an echo-dense lesion in the optic nerve head. There was increased uptake of the right lacrimal gland and presence of ‘Panda sign’ with Gallium scan. A diagnosis of right ocular sarcoidosis was made base on the clinical features and Gallium scan.

Ismail, Shatriah; Embong, Zunaina; Hitam, Wan Hazabbah Wan

2005-01-01

171

Synthesis and characterization of gallium colloidal nanoparticles  

Microsoft Academic Search

In this work, gallium colloidal nanoparticles (Ga-Nps) were synthesized by chemical liquid deposition (CLD). This method involved the deposition of metallic atoms with organic solvents (THF, acetone and 2-propanol) in a freezing matrix of the solvent at 77K, in order to obtain core–shell Ga-Nps which were characterized by: FT-IR, UV–Vis, TEM, SAED and electrophoretic mobility measurements. TEM images revealed a

M. F. Meléndrez; G. Cárdenas; J. Arbiol

2010-01-01

172

Growth and characterization of gallium nitride nanowire  

Microsoft Academic Search

The present-day trend towards the development of nanostructures has resulted in several interesting material systems with unique and, in some cases, novel properties. Gallium nitride nanowires and nanodimensional structures have been realized using a simpler approach of vapour phase-assisted deposition.GaN nanodimensional structures have been realized on (0001) sapphire substrates by suitable surface treatment procedure using ferrous salt. Growth has been

Vipul Srivastava; V. Sureshkumar; P. Puviarasu; K. Thangaraju; R. Thangavel; J. Kumar

2005-01-01

173

The Baksan gallium solar neutrino experiment  

SciTech Connect

A radiochemical /sup 71/Ga-/sup 71/Ge experiment to determine the integral flux of neutrinos from the sun has been constructed at the Baksan Neutrino Observatory in the USSR. Measurements have begun with 30 tonnes of gallium. The experiment is being expanded with the addition of another 30 tonnes. The motivation, experimental procedures, and present status of this experiment are presented. 43 refs., 1 fig., 1 tab.

Gavrin, V.N.; Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Girin, S.V.

1989-01-01

174

Gallium-67 imaging in muscular sarcoidosis  

SciTech Connect

A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

1984-07-01

175

Peculiarities of gallium crystallization in confined geometry  

Microsoft Academic Search

The freezing and melting phase transitions for gallium embedded into a porous glass with a pore size of about 8 nm were studied\\u000a using acoustic, NMR, and x-ray techniques. It was shown that the broadened solidification and melting transitions upon deep\\u000a cooling up to complete freezing at 165 K were due to the formation of ?-Ga within pores. The offset

B. F. Borisov; E. V. Charnaya; A. V. Gartvik; Cheng Tien; Yu. A. Kumzerov; V. K. Lavrentev

2004-01-01

176

Structural studies on synthesised gallium nitride  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) powder has been synthesised through reaction between metal gallium and ammonia (NH 3) in a resistively heated quartz reactor. Experiments have been performed for various reaction temperatures (range 900-950°C) and reaction periods (4-12 h). The optimised reaction temperature and period are 950°C and 8 h, respectively. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) studies have been carried out on the synthesised GaN powder for different growth conditions and the results have been correlated. XRD pattern reveals that the synthesised GaN is of a single-phase wurtzite structure. The calculated lattice parameter values are a=3.186 Å and c=5.174 Å. XRD pattern for the samples prepared for the reaction period of less than 8 h exhibit GaN peaks along with gallium oxide (Ga 2O 3) peaks. The change in the surface features with respect to the reaction period has been investigated using SEM.

Senthil Kumar, M.; Ramasamy, P.; Kumar, J.

2000-04-01

177

Compensation and Characterization of Gallium Arsenide  

NASA Astrophysics Data System (ADS)

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the shallow silicon donors are compensated by deep acceptors. Copper is an example of a transition metal that forms deep acceptors in GaAs, and therefore this work will focus on the compensation and characterization of GaAs:Si:Cu. The compensation of the material has shown that the lower diffusion temperatures (500-600^ circC) form primarily the well-known Cu _{rm B} centers whereas the higher temperature anneals (>750 ^circC) result in the formation of CU_{rm A}. Using compensation curves, the copper density is found by comparing the compensation temperature with copper solubility curves given by others. These curves also show that the formation of CU_{rm B}, EL2, and CU_{rm A} can be manipulated by varying processing parameters such as annealing temperature and arsenic pressure. The compensation results are confirmed using Temperature-Dependent Hall (TDH) measurements to detect the copper levels. Also, the photoconductive properties of the material under illumination from 1.06 and 2.1 ?m wavelength laser pulses have been used to demonstrate the effects of the different processing procedures. The persistent photoconductivity inherent to these devices under illumination from the 1.06 ?m laser pulse is used to predict the concentration of the Cu_ {rm B}<=vel, and the fast hole capture times of the various acceptors are found through the response to a 140 ps (FWHM), 2.1 ?m laser pulse. Finally, the physical distribution of the copper atoms in the gallium arsenide wafer is examined using Glow Discharge and Secondary Ion Mass Spectroscopy (GDMS and SIMS). These techniques have been used to show that the copper diffusion in gallium arsenide is non-uniform with respect to depth and surface position.

Roush, Randy Allen

1995-01-01

178

Effect of Gallium Nitrate on Experimental Autoimmune Uveitis  

Microsoft Academic Search

Gallium nitrate (GN) has been shown to inhibit T cell-mediated inflammatory disease. The purpose of our study was to test the effect of gallium nitrate (GN) on experimental autoimmune uveitis (EAU). Experimental autoimmune uveitis was induced in male Lewis rats immunized with retinal S-antigen. Rats received subcutaneous injections of GN or saline one day prior to immunization and 1, 4,

MARK C. LOBANOFF; ALEXANDER T. KOZHICH; DANIEL I. MULLET; NICHOLAS GERBER; IGAL GERY; CHI-CHAO CHAN; SCOTT M. WHITCUP

1997-01-01

179

Adsorption of Gallium with N503 Levextrel Resin.  

National Technical Information Service (NTIS)

The adsorptivity of N503 (N, N-di(sec-octyl)acetamide) levextrel resin to gallium in the HCl medium was studied. The absorption rate and absorption isotherm of the resin to gallium were measured. The results show that the absorption of the resin to galliu...

J. R. Chen J. Hu C. Peng

1995-01-01

180

P-n junctions formed in gallium antimonide  

NASA Technical Reports Server (NTRS)

Vapor phase deposition process forms a heavily doped n-region on a melt-grown p-type gallium antimonide substrate. HCl transports gallium to the reaction zone, where it combines with antimony hydride and the dopant carrier, hydrogen telluride. Temperatures as low as 400 degrees C are required.

Clough, R.; Richman, D.; Tietjen, J.

1970-01-01

181

First results from the Soviet-American Gallium Experiment.  

National Technical Information Service (NTIS)

The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is co...

A. I. Abazov D. N. Abdurashitov O. L. Anosov L. A. Eroshkina E. L. Faizov

1990-01-01

182

Myopericarditis in acquired immunodeficiency syndrome diagnosed by gallium scintigraphy  

SciTech Connect

Myocarditis is among the cardiac complications of acquired immunodeficiency syndrome and, yet, is often not discovered until autopsy. Gallium scintigraphy has been employed in diagnosing this entity, but few data are available about its diagnostic accuracy and value. Here, the authors report two cases of myopericarditis as diagnosed by gallium scan.

Cregler, L.L.; Sosa, I.; Ducey, S.; Abbey, L. (Bronx VA Medical Center, NY (USA))

1990-07-01

183

Two octanuclear gallium metallamacrocycles of topologically different connectivities.  

PubMed

Two topologically different metallamacrocycles--S8 symmetric octanuclear gallium(III) metalladiazamacrocycle and pseudo-D4 symmetric octanuclear gallium(III) metalladiazamacrocycle--could be prepared using two similar heteroditopic bridging ligands having asymmetrical tridentate-bidentate binding residues. PMID:18026590

Park, Mira; John, Rohith P; Moon, Dohyun; Lee, Kyungjin; Kim, Ghyung Hwa; Lah, Myoung Soo

2007-12-14

184

Early Gallium-67 abdominal imaging: pitfalls due to bowel activity  

SciTech Connect

In gallium scanning for abdominal inflammatory disease, early imaging has been advocated so physiological activity within the bowel will not be confused with pathologic uptake. The normal physiologic pattern of bowel uptake is not desribed in the literature. Our study was undertaken to evaluate the frequency and patterns of gallium-67 bowel activity which may occur when early imaging is performed.

Perkins, P.J.

1981-05-01

185

NEUTRON-ACTIVATION STUDY OF GALLIUM ARSENIDE CONTAMINATION BY QUARTZ  

Microsoft Academic Search

Gallium arsenide crystals were synthesized by the horizontal Bridgman ; method in neutron-activated boats of natural and synthetic fused quartz. ; lnstrumental radiochemical techniques were applied to determine the silicon ; concentrations from Si³¹ radioactivity measurements and to identify other ; trace elements transferred to the gallium arsenide during the process. All ; crystals were found completely enveloped in an

Werner Kern

1962-01-01

186

Indium Gallium Nitride Multijunction Solar Cell Simulation Using Silvaco Atlas.  

National Technical Information Service (NTIS)

This thesis investigates the potential use of wurtzite Indium Gallium Nitride as photovoltaic material. Silvaco Atlas was used to simulate a quad-junction solar cell. Each of the junctions was made up of Indium Gallium Nitride. The band gap of each juncti...

B. Garcia

2007-01-01

187

Laser photochemistry of gallium-containing compounds. [Trimethylgallium  

SciTech Connect

The production of gas-phase gallium atoms in the photolysis of trimethylgallium has been investigated at 193 nm and at other laser wavelengths. Ground state (4 /sup 2/P/sup 0//sub 1/2) and metastable (4 /sup 2/P/sup 0//sub 3/2/) gallium atoms are detected using laser-induced fluorescence techniques. Our results indicate that gallium atoms continue to be produced at long times after the laser pulse. The observed dependence on photolysis laser fluence, trimethylgallium pressure, and buffer gas pressure are consistent with a mechanism in which highly excited gallium methyl radicals undergo unimolecular decomposition to produce gallium atoms. Since this process is observed to happen on the time scale of hundreds of microseconds, these results have important implications for studies of metal deposition and direct laser writing by laser photolysis of organometallic compounds. 31 refs., 5 figs.

Baughcum, S.L.; Oldenborg, R.C.

1986-01-01

188

On the Formation Kinetics of Gallium Spinels . Zur Bildungskinetik von Gallium-Spinellen.  

National Technical Information Service (NTIS)

The reaction mechanism for gallium spinel formation is studied through interactions between NiO, MgO or CoO with Ga2O3 at 1230 to 1550 C. X-ray and phase transformation observations show that: (1) NiGa2O2 is formed by the transport of Ni(2+) and O(2-) thr...

W. Laqua

1971-01-01

189

Composite droplets: evolution of InGa and AlGa alloys on GaAs(100).  

PubMed

We present a comparative study for the evolution of utilizing indium gallium (InGa) and aluminum gallium (AlGa) alloys fabricated on GaAs(100) by means of simultaneous and sequential droplet formation. The composite alloys reported using the sequential approach lack the ability to precisely determine the final alloy composition as well as consistency in the density of the droplets. Further, the composition of the InGa alloy is not uniform, as seen by the size distribution using an atomic force microscope (AFM). Although this approach may be acceptable for materials with similar surface kinetics, as in the case of AlGa, it is not acceptable for InGa. This investigation reveals that the simultaneous approach for fabricating composite alloys is the optimum approach for producing InGa alloys with better control on composition for plasmonic applications such as plasmonic waveguides. PMID:21817741

Sablon, K A; Wang, Zh M; Salamo, G J

2008-03-26

190

Gallium scintigraphic pattern in lung CMV infections  

SciTech Connect

Due to extensive use of prophylactic therapy for Pneumonitis Carinii Pneumonia (PCP), Cytomegalic Viral (CMV) infection may now be the most common lung infection in AIDS patients. This study was performed to determine Gallium-67 patterns in AIDS patients with CMV. Pathology reports were reviewed in AIDS patients who had a dose of 5 to 10 mCi of Gallium-67 citrate. Analysis of images were obtained 48-72 hours later of the entire body was performed. Gallium-67 scans in 14 AIDS patients with biopsy proven CMV, were evaluated for eye, colon, adrenal, lung and renal uptake. These were compared to 40 AIDS patients without CMV. These controls had infections including PCP, Mycobacterial infections, and lymphocytic interstitial pneumonitis. 100% of CMV patients had bowel uptake greater than or equal to liver. Similar bowel activity was seen in 50% of AIDS patients without CMV. 71% had intense eye uptake which was seen in only 10% of patients without CMV. 50% of CMV patients had renal uptake compared to 5% of non-CMV cases. Adrenal uptake was suggested in 50%, however, SPECT imaging is needed for confirmation. 85% had low grade lung uptake. The low grade lung had perihilar prominence. The remaining 15% had high grade lung uptake (greater than sternum) due to superimposed PCP infection. Colon uptake is very sensitive indicator for CMV infection. However, observing eye, renal, and or adrenal uptake improved the diagnostic specificity. SPECT imaging is needed to confirm renal or adrenal abnormalities due to intense bowel activity present in 100% of cases. When high grade lung uptake is seen superimposed PCP is suggested.

Ganz, W.I.; Cohen, D.; Mallin, W. [Univ. of Miami School of Medicine, FL (United States)] [and others

1994-05-01

191

Patterned gallium surfaces as molecular mirrors.  

PubMed

An entirely new means of printing molecular information on a planar film, involving casting nanoscale impressions of the template protein molecules in molten gallium, is presented here for the first time. The metallic imprints not only replicate the shape and size of the proteins used as template. They also show specific binding for the template species. Such a simple approach to the creation of antibody-like properties in metallic mirrors can lead to applications in separations, microfluidic devices, and the development of new optical and electronic sensors, and will be of interest to chemists, materials scientists, analytical specialists, and electronic engineers. PMID:17689239

Bossi, Alessandra; Rivetti, Claudio; Mangiarotti, Laura; Whitcombe, Michael J; Turner, Anthony P F; Piletsky, Sergey A

2007-09-30

192

Gallium-67 imaging in muscular sarcoidosis  

SciTech Connect

A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid muscle disease but is consistent with the rarity of clinical evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

1984-07-01

193

Gallium induces the production of virulence factors in Pseudomonas aeruginosa.  

PubMed

The novel antimicrobial gallium is a nonredox iron III analogue with bacteriostatic and bactericidal properties, effective for the treatment of Pseudomonas aeruginosa in vitro and in vivo in mouse and rabbit infection models. It interferes with iron metabolism, transport, and presumably its homeostasis. As gallium exerts its antimicrobial effects by competing with iron, we hypothesized that it ultimately will lead cells to an iron deficiency status. As iron deficiency promotes the expression of virulence factors in vitro and promotes the pathogenicity of P. aeruginosa in animal models, it is anticipated that treatment with gallium will also promote the production of virulence factors. To test this hypothesis, the reference strain PA14 and two clinical isolates from patients with cystic fibrosis were exposed to gallium, and their production of pyocyanin, rhamnolipids, elastase, alkaline protease, alginate, pyoverdine, and biofilm was determined. Gallium treatment induced the production of all the virulence factors tested in the three strains except for pyoverdine. In addition, as the Ga-induced virulence factors are quorum sensing controlled, co-administration of Ga and the quorum quencher brominated furanone C-30 was assayed, and it was found that C-30 alleviated growth inhibition from gallium. Hence, adding both C-30 and gallium may be more effective in the treatment of P. aeruginosa infections. PMID:24151196

García-Contreras, Rodolfo; Pérez-Eretza, Berenice; Lira-Silva, Elizabeth; Jasso-Chávez, Ricardo; Coria-Jiménez, Rafael; Rangel-Vega, Adrián; Maeda, Toshinari; Wood, Thomas K

2014-02-01

194

Assessment of gallium-67 scanning in pulmonary and extrapulmonary sarcoidosis  

SciTech Connect

Gallium-67 scans have been widely employed in patients with sarcoidosis as a means of indicating alveolitis and the need for corticosteroid therapy. Observation of 32 patients followed 3 or more years after gallium scans showed no correlation between findings and later course: of 10 patients with pulmonary uptake, 7 recovered with minor residuals; of 18 patients with mediastinal of extrathoracic uptake, 10 had persistent or progressive disease; of 4 patients with negative initial scans, 2 had later progression. The value of gallium-67 scans as an aid to diagnosis was studied in 40 patients with extrapulmonary sarcoidosis. In 12 patients, abnormal lacrimal, nodal, or pulmonary uptake aided in selection of biopsy sites. Gallium-67 scans and serum ACE levels were compared in 97 patients as indices of clinical activity. Abnormal gallium-67 uptake was observed in 96.3% of the tests in active disease, and ACE level elevation occurred in 56.3%. In 24 patients with inactive or recovered disease, abnormal gallium-67 uptake occurred in 62.5% and ACE level elevation in 37.5%. Gallium-67 scans have a limited but valuable role in the diagnosis and management of sarcoidosis.

Israel, H.L.; Gushue, G.F.; Park, C.H.

1986-01-01

195

Doped gallium oxide nanowires for photonics  

NASA Astrophysics Data System (ADS)

Monoclinic gallium oxide, ?-Ga2O3, is a transparent conducting oxide (TCO) that presents one of the widest band gaps among this family of materials. Its characteristics make it highly interesting for applications in UV - visible - IR optoelectronic and photonic devices. On the other hand, the morphology of nanowires made of this oxide presents specific advantages for light emitting nanodevices, waveguides and gas sensors. Control of doping of the nanostructures is of the utmost importance in order to tailor the behavior of these devices. In this work, the growth of the nanowires is based on the vapor-solid (VS) mechanism during thermal annealing treatment while the doping process was carried out in three different ways. In one of the cases, doping was obtained during the growth of the wires. A second method was based on thermal diffusion of the dopants after the growth of undoped nanowires, while the third method used ion implantation to introduce optically active ions into previously grown nanowires. The study of the influence of the different dopants on the luminescence properties of gallium oxide nanowires is presented. In particular, transition metals and rare earths such as Cr, Gd, Er or Eu were used as optically active dopants that allowed selection of the luminescence wavelength, spanning from the UV to the IR ranges. The benefits and drawbacks of the three different doping methods are analyzed. The waveguiding behavior of the doped nanowires has been studied by room temperature micro-photoluminescence.

Nogales, E.; López, I.; Méndez, B.; Piqueras, J.; Lorenz, K.; Alves, E.; García, J. A.

2012-02-01

196

Gallium scanning in lymphoid interstitial pneumonitis of children with AIDS  

SciTech Connect

Lymphoid interstitial pneumonitis (LIP) is a frequent pulmonary complication in the child with the acquired immune deficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection. We report the gallium scan findings in two children with AIDS and LIP. Gallium scintigraphy in both children demonstrated increased radionuclide concentration throughout the lungs, a pattern indistinguishable scintigraphically from that of Pneumocystis carinii pneumonia (PCP). This should alert nuclear medicine practitioners and referring physicians to another cause of diffusely increased gallium uptake in the lungs of patients with AIDS.

Schiff, R.G.; Kabat, L.; Kamani, N.

1987-12-01

197

Novel gallium(III) phthalocyanine derivatives – Synthesis, photophysics and photochemistry  

Microsoft Academic Search

The syntheses of gallium(III) chloride phthalocyanine {(Cl)GaPc}, octaphenoxyphthalocyaninato gallium(III) chloride {(Cl)GaOPPc} and octakis(4-tert-butylphenoxy)phthalocyaninato gallium(III) chloride {(Cl)GaOTBPPc}; as well as their photophysical and photochemical parameters are hereby presented. Fluorescence quantum yields do not vary much among the three metallophthalocyanines (MPcs); therefore it was concluded that the effect of the substituents is not significant amongst (Cl)GaPc, (Cl)GaOPPc and (Cl)GaOTBPPc. Solvents effects, however,

Vongani Chauke; Abimbola Ogunsipe; Mahmut Durmu?; Tebello Nyokong

2007-01-01

198

Measurement of the solar neutrino capture rate with gallium metal  

SciTech Connect

The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2{sub {minus}7.0{minus}3.0}{sup +7.2+3.5} SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted standard solar model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting of {sup 71}Ge, and data analysis, are discussed in detail. {copyright} {ital 1999} {ital The American Physical Society}

SAGE Collaboration

1999-11-01

199

High efficiency luminescent gallium nitride powders by direct synthesis from gallium metal and ammonia.  

NASA Astrophysics Data System (ADS)

High quality as-synthesized gallium nitride (GaN) powders have been obtained by a complete reaction between high purity gallium metal and ultra high purity ammonia in a horizontal quartz tube reactor at 1100 ºC. Elemental analysis showed that the powders obtained by this method have a stoichiometric nitrogen concentration (16.73 weight hexagonal crystalline structure of the GaN synthesized. Electron microscopy showed that the powders are formed by at least two kinds of particles, small size platelets and large size needles. The GaN powders obtained by this method are light gray and produce high ultra-violet luminescence around 370 nm (3.35 eV, near band-edge emission) when they are excited by accelerated electrons (cathodoluminescence) or by high energy photons (photoluminescence) at room temperature.

Garcia, Rafael; Bell, Abigail; Stevens, Michael; Ponce, Fernando

2003-10-01

200

Infrared Response of Impurity Doped Silicon MOSFET's (IRFET's): Fabrication and Characterization of the Gallium Doped Infrared Sensing MOSFET.  

National Technical Information Service (NTIS)

Fabrication and characterization of the gallium doped infrared sensing MOSFET is described. Gallium doped MOSFET device structures have been fabricated by diffusion of gallium from doped oxide sources into n-channel MOSFET's fabricated on a normal boron p...

L. Forbes

1976-01-01

201

Characteristics of Gallium-Substituted Hexagonal Mesoporous Silica: Effects of Gallium Content  

Microsoft Academic Search

Gallium-substituted hexagonal mesoporous silicas (Ga-HMS) with various Si\\/Ga ratios in the range of 15 and 200 were prepared at ambient temperature by neutral surfanctant templating pathway. The materials were synthesized by using dodecylamine as a template and tetraethylorthosilicate as a silicon source. They were characterized by energy dispersive X-ray spectroscopy, powder X-ray diffraction (XRD), N2 adsorption-desorption, thermogravimetric analysis, differential scanning

Hsin-Yu Lin; Yu-Lin Pan; Yu-Wen Chen

2005-01-01

202

Microencapsulation of gallium-indium (Ga-In) liquid metal for self-healing applications.  

PubMed

Microcapsules containing a liquid metal alloy core of gallium-indium (Ga-In) are prepared via in situ urea-formaldehyde (UF) microencapsulation. The capsule size, shape, thermal properties, and shell wall thickness are investigated. We prepare ellipsoidal capsules with major and minor diameter aspect ratios ranging from 1.64 to 1.08 and with major diameters ranging from 245?µm to 3?µm. We observe that as the capsule major diameter decreases, the aspect ratio approaches 1. The thermal properties of the prepared microcapsules are investigated by thermogravimetric (TGA) and differential scanning calorimetry (DSC). Microcapsules are shown to survive incorporation into an epoxy matrix and to trigger via mechanical damage to the cured matrix. Microcapsules containing liquid metal cores may have diverse applications ranging from self-healing to contrast enhancement or the demonstration of mechano-adaptive circuitry. PMID:24495196

Blaiszik, B J; Jones, A R; Sottos, N R; White, S R

2014-01-01

203

Density functional study of the effects of doping and stoichiometry on gallium diffusion in gallium arsenide  

NASA Astrophysics Data System (ADS)

Previous experimental [1-4] and theoretical [5,6] work on the properties of diffusion of gallium within gallium arsenide has produced some results that are apparently at odds with each other. We present results of a wide theoretical survey of the point defects that form in this material with special attention paid to the formation and diffusion of excess-gallium-related point defects. In this study we applied density functional theory in the local density approximation [7]. Diffusion was examined through the use of the nudged elastic band method [8]. After considering the accuracy of the approximations used, the calculations yield information compatible with the experimental situation and capable of shedding light on areas of apparent disagreement.[4pt] [1] G B"osker et al., Phys. Rev. B 52, 11927 (1995). [2] G B"osker et al., J. Appl. Phys. 86, 791 (1999). [3] H Bracht and S Brotzmann, Phys. Rev. B 71, 115216 (2005). [4] H Bracht et al., Physica B 308-210, 831 (2001). [5] K Levasseur-Smith and N. Mousseau, J. Appl. Phys. 103, 113502 (2008). [6] PA Schultz et al., Mod. and Sim. in Mat. Sci. and Engr. 17, 084007 (2009). [7] G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993); ibid. 49, 14251 (1994). [8] H. J'onsson et al., "Classical and quantum dynamics in condensed phase systems," (World Scientific, 1998) Chap. 16, pp. 385-404.

Schick, J. T.; Morgan, C. G.

2011-03-01

204

Effects of Neutron Radiation on Aluminum-Gallium-Arsenide Lasers.  

National Technical Information Service (NTIS)

Double heterojunction aluminum-gallium-arsenide laser diodes were irradiated in a nuclear reactor to determine the effects of neutron radiation. Two types of lasers were used; both types of diodes showed significant decreases in power output at neutron fl...

T. E. Walsh

1978-01-01

205

Optical Characterization of Thick Growth Orientation-Patterned Gallium Arsenide.  

National Technical Information Service (NTIS)

Tunable laser sources in the mid-infrared (MIR) spectral range are required for several Air Force applications. Orientation patterned gallium arsenide (OPGaAs) is a promising nonlinear conversion material because it has broad transparency and can be engin...

J. W. Meyer

2006-01-01

206

Preliminary Experimental Measurements for a Gallium Electromagnetic (GEM) Thruster  

NASA Technical Reports Server (NTRS)

A low-energy gallium plasma source is used to perform a spatially and temporally broad spectroscopic survey in the 220-520 nm range. Neutral, singly, and doubly ionized gallium are present in a 20 J, 1.8 kA (peak) arc discharge operating with a central cathode. When the polarity of the inner electrode is reversed the discharge current and arc voltage waveforms remain similar. Utilizing a central anode configuration, multiple Ga lines are absent in the 270-340 nm range. In addition, neutral and singly ionized Fe spectral lines are present, indicating erosion of the outer electrode. With graphite present on the insulator to facilitate breakdown, line emission from the gallium species is further reduced and while emissions from singly and doubly ionized carbon atoms and molecular carbon (C2) radicals are observed. These data indicate that a significant fraction of energy is shifted from the gallium and deposited into the various carbon species.

Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

2007-01-01

207

Sodium Gallium Oxide Electrolyte Additive for Aluminum Anode Activation.  

National Technical Information Service (NTIS)

An additive for an aluminum-based semi-fuel cell system includes a combination of components including gallium, oxygen, and a sodium component dissolvable an alkaline electrolyte solution such as seawater and sodium hydroxide. These components form sodium...

L. G. Carreiro S. P. Tucker

2001-01-01

208

Simulating the atomic assembly of gallium arsenide  

NASA Astrophysics Data System (ADS)

A molecular dynamics (MD) atomistic modeling and simulation approach was used to study the assembly mechanisms of homoepitaxial GaAs vapor deposition as a function of temperature and flux composition. This requires interatomic potentials that are able to reasonably predict the structures and energies of small clusters, bulk crystal lattices, and surface binding. The majority of the literature potentials could not be used in the MD simulation environment. However, the Tersoff and Stillinger-Weber (SW) potential formats could be utilized and their parametrizations were systematically evaluated. Although the Tersoff potential had very good bulk and molecular arsenic properties, the potential could not be used to study vapor deposition because it had an unphysically high As2 desorption probability over a wide range of surface temperatures. The SW potential modeled the zinc blende GaAs structure quite well; however, bonding environments with As-As and Ga-Ga interactions were poorly modeled. This limited the application of the SW potential to the study of the low-temperature atomic assembly of GaAs thin films with an equiatomic vapor. None of the compound semiconductor potentials available in literature correctly predicted the experimentally-observed surface reconstructions. A simple method for accounting for the electron occupancies of dangling bonds was proposed and was successfully used to investigate the energetics of various atomic-scale structures on the GaAs (001) surface. An analytic, bond-order potential (BOP) was proposed that improved upon many of the shortcomings of the previous potentials. The potential was derived from a tight-binding description of bonding in a manner that addresses the valence-dependent character of heteroatomic primary and secondary bonding. The structural and binding energy trends predicted by the BOP were found to match experimental observations and ab initio calculations. The homoepitaxial assembly of atomic gallium and molecular As2 on a (001) GaAs surface was also shown to phenomenologically reproduce experimental trends. The initial atomic assembly interaction dynamics were studied on gallium-terminated and arsenic-terminated surfaces. A number of intermediate binding states were directly observed during the surface diffusion of arsenic dimers on the gallium-terminated surface. Desorption, rather than diffusion, was the dominant mechanism on the arsenic-terminated surface.

Murdick, Dewey Andrew

209

Detection of deep venous thrombophlebitis by gallium 67 scintigraphy  

SciTech Connect

Deep venous thrombophlebitis may escape clinical detection. Three cases are reported in which whole-body gallium 67 scintigraphy was used to detect unsuspected deep venous thrombophlebitis related to indwelling catheters in three children who were being evaluated for fevers of unknown origin. Two of these children had septicemia from Candida organisms secondary to these venous lines. Gallium 67 scintigraphy may be useful in the detection of complications of indwelling venous catheters.

Miller, J.H.

1981-07-01

210

Growth and characterization of indium antimonide and gallium antimonide crystals  

Microsoft Academic Search

Indium antimonide and gallium antimonide were synthesized from the respective component elements using an indigenously fabricated\\u000a synthesis unit. Bulk crystals of indium antimonide and gallium antimonide were grown using both the vertical and horizontal\\u000a Bridgman techniques. Effect of ampoule shapes and diameters on the crystallinity and homogeneity was studied. The grown crystals\\u000a were characterized using X-ray analysis, EDAX, chemical etching,

N. K. Udayashankar; H. L. Bhat

2001-01-01

211

Electrical contacts to ion cleaned n-type gallium arsenide.  

NASA Technical Reports Server (NTRS)

The electrical current through silver contacts evaporated onto n-type gallium arsenide is reported as a function of surface treatment. Contacts to untreated gallium arsenide exhibit the expected high resistance. Surface cleaning by argon ion bombardment reduces the resistance by three orders of magnitude. The electrical resistance beyond 850 eV increases rapidly with ion bombardment energy. The resistance minimum at 850 eV is explained semiquantitatively in terms of a balance between cleaning and surface damage.

Walker, G. H.; Conway, E. J.

1972-01-01

212

Characteristics of the Gallium-doped infrared sensing MOSFET (IRFET)  

Microsoft Academic Search

Gallium-doped infrared sensing MOSFET's have been operated in the far infrared, 8- to 14-µm wavelength region with a quantum efficiency of 2.8 percent and a responsivity of 3.5 × 103A\\/J. A strong field enhancement has been observed in both thermal and optical emission of holes from the neutral gallium center in silicon. Application considerations in large-scale infrared imaging arrays are

K. W. Loh; B. M. Hawkins; H. Elabd; L. Forbes

1977-01-01

213

Selective catalytic reduction of NO with methane on gallium catalysts  

Microsoft Academic Search

Gallium species supported on H-ZSM-5 and on H-mordenite are active catalysts for NO reduction with methane in the presence of excess O[sub 2]. Over Ga-H-ZSM-5, the NO reduction rate is first order in NO with a variable, fractional order in CH[sub 4]. The distinct feature of these gallium-based catalysts is their very high CH[sub 4] selectivities for NO[sub x] reduction.

Yuejin Li; J. N. Armor

1994-01-01

214

Complexometric determination of gallium with calcein blue as indicator  

USGS Publications Warehouse

A metalfluorechromic indicator, Calcein Blue, has been used for the back-titration of milligram amounts of EDTA in presence of gallium complexes. The indicator was used in conjunction with an ultraviolet titration assembly equipped with a cadmium sulphide detector cell and a microammeter for enhanced end-point detection. The result is a convenient and rapid method with an accuracy approaching 0.1 % and a relative standard deviation of about 0.4% for 10 mg of gallium. ?? 1967.

Elsheimer, H. N.

1967-01-01

215

On-chip superconductivity via gallium overdoping of silicon  

Microsoft Academic Search

We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In

R. Skrotzki; J. Fiedler; T. Herrmannsdörfer; V. Heera; M. Voelskow; A. Mücklich; B. Schmidt; W. Skorupa; G. Gobsch; M. Helm; J. Wosnitza

2010-01-01

216

X ray topography study of gallium phosphate crystals and resonators  

Microsoft Academic Search

Using the synchrotron radiation delivered by the DCI storage ring at LURE (Orsay, France), the X-ray topography technique was used to study the crystalline perfection of GaPO4 samples grown under different conditions. The growth of gallium phosphate on a berlinite seed is analyzed by X-ray section topography. The results obtained demonstrate the feasibility of gallium phosphate epitaxy on large berlinite

B. Capelle; A. Zarka; J. Schwartzel; J. Detaint; Y. Zheng; A. Ibanez; E. Philippot

1993-01-01

217

Bone modeling in gallium nitrate-treated rats  

Microsoft Academic Search

Summary  Gallium nitrate (GaN) reduces cancer-related hypercalcemia and inhibits bone resorptionin vitro. This study investigated the effects of chronic GaN administration on bone, kidney, and parathyroid gland activity of growing\\u000a rats. Experimental animals received GaN (1.75 mg elemental gallium i.p. QOD×8, Ga+), and controls received the solvent (Ga?). In the bone of Ga+ rats the number of osteoclasts was increased (Ga+:

G. Cournot-Witmer; A. Bourdeau; M. Lieberherr; C. L. Thil; J. J. Plachot; G. Enault; R. Bourdon; S. Balsan

1987-01-01

218

Visualization study of melting and solidification in convecting hypoeutectic GaIn alloy  

Microsoft Academic Search

Natural convection flow visualization experiments during melting and solidification of a hypoeutectic gallium five weight percent indium were performed using a real time X-ray radioscopy technique. The experiments revealed a conductive-convective threshold for the onset of natural convection in the alloy. The threshold appears to be caused by a substantial chemical stratification of indium in the melt. The observed gravitational

R. Derebail; J. N. Koster

1998-01-01

219

Gallium-69, 71 and nitrogen-14 nuclear magnetic resonance of amorphous gallium nitride  

NASA Astrophysics Data System (ADS)

This work reports results of nuclear magnetic resonance experiments on amorphous gallium nitride (a-GaN) made via room-temperature-MBE deposition on sapphire and aluminum-foil substrates. The amorphous gallium nitride made in this way has been compared with powdered-crystal GaN (px-GaN). The temperature dependence of spin-lattice relaxation time below room temperature was found to be similar, which indicates that the Debye temperature for a-GaN and crystal gallium nitride (x-GaN) may be similar. However, the actual spin-lattice relaxation times are much shorter in a-GaN. Several important distinctions between the materials are also clear. Amorphous gallium nitride has a very broad NMR lineshape, which has been determined to have been broadened by the second-order-quadrupole interaction and further inhomogenously broadened by chemical shifts. This work has also demonstrated that a-GaN's NMR signal results from the central transition of the I = 3/2 gallium nuclei. Using this information, estimates for the electric field gradients present in a-GaN have been obtained. A large distribution of EFG's has been inferred, including a significant fraction of sites experiencing EFG's much greater than those of single-crystal, hexagonal GaN. The spin-lattice relaxation times of a-GaN are two orders of magnitude shorter than those of x-GaN, and between one-fortieth and one-two-hundredth as long as T1's for px-GaN. This is likely due to the significance of local disorder modes (modeled as two-level systems) in the amorphous network, which provide more relaxation pathways than those available to the single-crystal sample. The spin-spin relaxation times of a-GaN have been found to be about 2/3 as long as those of px-GaN, possibly indicating that the disorder modes in a-GaN also play a role in the decay of transverse magnetization. An abundance of local disorder modes could explain the temperature dependence of the a-GaN lineshape and also its uniquely fast relaxation. These disorder modes may result from significant threefold coordination, which is predicted theoretically. The presence of threefold coordination can also explain the large range of EFG's observed in a-GaN.

Schuster, David Michael

220

Role of the gallium scan in Hodgkin's disease  

SciTech Connect

The reports of 240 gallium scans on 165 patients with Hodgkin's disease were reviewed to compare results with higher doses with those in earlier studies that employed lower doses. Tracer concentrations in specific sites were correlated with radiologic and pathologic reports and with the clinical courses of the patients studied. There were no significant differences in overall results between newer and older gallium scanning techniques. For untreated patients, the overall sensitivity was only 64%, but the overall specificity was 98%. For untreated patients and for patients with relapsing disease, the presence of gallium concentration in a specific site was highly predictive of active Hodgkin's disease at that site. However, for routine follow-up of treated patients, 95% of unsuspected relapses were missed by the scan, indicating the limited usefulness of negative scan results in this setting. For patients with residual abnormalities after therapy, demonstrated by other radiographic means, increased uptake of gallium in abdominal or peripheral lymph nodes also indicated active disease, although lack of uptake was reliable only in the mediastinum. Based on these results, it appears that the higher doses used in this study have not substantially improved the role of gallium scanning in this disease. Although it is potentially useful in providing confirmatory data at diagnosis or in patients with new or residual objective abnormalities after treatment, routine use of gallium scanning in Hodgkin's disease is not recommended.

Hagemeister, F.B.; Fesus, S.M.; Lamki, L.M.; Haynie, T.P. (Univ. of Texas, M.D. Anderson Cancer Center, Houston (USA))

1990-03-01

221

Hyperfine Magnetic Field Measurements in the Heusler Alloys COBALT(2)-TITANIUM-Z, COBALT(2)-MAGNESIUM-Z (z = Silicon, Germanium, and Tin) and COBALT(2)-MAGNESIUM- Gallium Using the Moessbauer Effect (me) and the Time Differential Perturbed Angular Correlation (tdpac) Techniques  

NASA Astrophysics Data System (ADS)

Measurements of the hyperfine magnetic field in a series of Heusler alloys were performed. The probes were in (^{119}Sn) and cadmium (^{111}Cd). These measurements were performed at the University of Cincinnati in Cincinnati, Ohio. Two techniques were used. The first technique was the Mossbauer effect, which was used to measure the hyperfine magnetic field on ^{119 }Sn in Co_2TiZ (Z = Si, Ge, and Sn), and the second technique was the Time Differential Perturbed Angular Correlation which was used to measure the hyperfine magnetic field on ^ {111}Cd in the Co_2MnZ (Z = Si, Ge, Sn, and Ga). The probes are expected to go to the Z sites of the alloys. The hyperfine magnetic field measurements on ^{119}Sn in Co _2TiZ (Z = Si, Ge, and Sn) alloys were done at room, dry ice and liquid nitrogen temperatures by using the Mossbauer effect technique. The data were fitted by using a least squares fit from which three parameters were extracted. These parameters are the isomer shift, the quadrupole splitting and the hyperfine magnetic field. Temperature variation measurements of the hyperfine magnetic field were performed on ^{111 }Cd in Co_2MnZ (Z = Si, Ge, Sn, and Ga) alloys. The data were fitted again by using a least squares fit from which the Larmor frequency which is related to the hyperfine magnetic field was extracted. Also the Fourier Transforms were taken of the data, on the one hand to confirm the results of the least squares fit and on the other hand to look for more frequencies. Results of the Fourier Transforms show that some of the probe, ^{111}In, did go to the Co site in the Co_2MnZ (Z = Ga, Si, and Ge) alloys. The hmf on ^{111 }Cd in the Co site of these alloys is found to be 68 kOe which is consistent with the value found in the literature. Two theoretical models were examined for the trends of hyperfine magnetic field on ^{119 }Sn and ^{111}Cd in Co_2MnZ (Z = Si, Ge, Sn, and Ga) alloys. These are the Campbell and Blandin model and the Stearns' overlap model. Results show that the Campbell and Blandin model does predict the trends of the hyperfine magnetic field on ^{111}Cd but it fails in predicting any trends on ^ {119}Sn in Co_2MnZ (Z = Si, Ge, Sn, and Ga) alloys. The overlap model did not predict any trends of hmf on either probe in these alloys. A new relationship was found between the hyperfine magnetic field and the lattice constants of these alloys.

Lahamer, Amer Said

1990-01-01

222

Cavity optomechanics in gallium phosphide microdisks  

NASA Astrophysics Data System (ADS)

We demonstrate gallium phosphide (GaP) microdisk optical cavities with intrinsic quality factors >2.8 × 105 and mode volumes <10(?/n)3, and study their nonlinear and optomechanical properties. For optical intensities up to 8.0 × 104 intracavity photons, we observe optical loss in the microcavity to decrease with increasing intensity, indicating that saturable absorption sites are present in the GaP material, and that two-photon absorption is not significant. We observe optomechanical coupling between optical modes of the microdisk around 1.5 ?m and several mechanical resonances, and measure an optical spring effect consistent with a theoretically predicted optomechanical coupling rate g0/2?˜30 kHz for the fundamental mechanical radial breathing mode at 488 MHz.

Mitchell, Matthew; Hryciw, Aaron C.; Barclay, Paul E.

2014-04-01

223

The Soviet-American Gallium Experiment (SAGE)  

SciTech Connect

It is a great pleasure for me to have been asked by Louis Rosen to tell you about the Soviet-American Gallium Experiment (SAGE). This undertaking is a multi-institutional collaboration among scientists from the Institute for Nuclear Research, Moscow (INR), Los Alamos National Laboratory (LANL), and several US universities. Its purpose is to measure the number of low-energy electron neutrinos emitted from the Sun that arrive at this planet. As such, it is an extremely important experiment, touching on fundamental physics issues as well as solar dynamics. In contrast to the strategic overviews, plans, and hopes for international collaboration presented earlier today, SAGE is an ongoing working effort with high hopes of producing the first measurement of the Sun's low-energy neutrino flux. This paper reviews this experiment. 3 refs., 3 figs.

Garvey, G.T.

1989-01-01

224

Cathodoluminescence spectra of gallium nitride nanorods  

PubMed Central

Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

2011-01-01

225

Gallium arsenide solar array subsystem study  

NASA Technical Reports Server (NTRS)

The effects on life cycle costs of a number of technology areas are examined for a gallium arsenide space solar array. Four specific configurations were addressed: (1) a 250 KWe LEO mission - planer array; (2) a 250 KWe LEO mission - with concentration; (3) a 50 KWe GEO mission planer array; (4) a 50 KWe GEO mission - with concentration. For each configuration, a baseline system conceptual design was developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies were then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance, and hence life cycle costs.

Miller, F. Q.

1982-01-01

226

Gallium Arsenide solar cell radiation damage experiment  

NASA Technical Reports Server (NTRS)

Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

Maurer, R. H.; Kinnison, J. D.; Herbert, G. A.; Meulenberg, A.

1991-01-01

227

Specific Heat Capacity of Gallium Nitride  

NASA Astrophysics Data System (ADS)

The specific heat capacity of gallium nitride (GaN) was measured for polycrystalline powder and single crystal samples. We present the temperature dependence of the specific heat capacity for single crystal and powdered GaN from 100 to 1300 K. The difference between the polycrystalline powder and single crystal arises from thermal evaporation in the high-temperature region, and this depends on the degree of heat transfer at 100--200 K. The temperature dependence of the specific heat capacity in the form cp = 7.1380 × 10-17T6 - 2.9836 × 10-13T5 + 4.2185 × 10-10T4 - 1.5068 × 10-7T3 - 1.6713 × 10-4T2 + 0.1774T - 1.3545 (J mol-1 K-1) was derived from a least squares fitting routine.

Lee, Sanghyun; Kwon, Su Yong; Ham, Hye Jeong

2011-11-01

228

Merits of gallium nitride based power conversion  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) based power electronics devices are actively being evaluated to determine if their theoretical advantages over silicon (Si) based switches can translate into improved performance of existing hardware as well as open the doors to new types of applications, such as high temperature implementations, or very high frequency power conversion. The following paper presents an overview of this activity. A brief summary about power electronics and the requirements of semiconductor devices used in this field is provided. Detailed analysis of the advantages and the challenges of using GaN devices is included along with a survey of demonstrations. This work also presents the test results from the evaluation of GaN devices from Efficient Power Conversion (EPC) and Transphorm. Included is a demonstration of EPC’s devices in a high frequency, high efficiency, switched-capacitor voltage doubler. This circuit achieves an output of 480 W at a switching frequency of 893 kHz.

Scott, Mark J.; Fu, Lixing; Zhang, Xuan; Li, Jinzhu; Yao, Chengcheng; Sievers, Markus; Wang, Jin

2013-07-01

229

Direct band gap wurtzite gallium phosphide nanowires.  

PubMed

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555-690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

Assali, S; Zardo, I; Plissard, S; Kriegner, D; Verheijen, M A; Bauer, G; Meijerink, A; Belabbes, A; Bechstedt, F; Haverkort, J E M; Bakkers, E P A M

2013-04-10

230

A threshold for onset of natural convection in binary metallic alloys  

Microsoft Academic Search

Experiments were performed with a new radioscopic flow visualization technique on natural convection during melting of a\\u000a binary metallic Ga-In alloy. This technique provides visualization of the density fields within opaque low Prandtl number\\u000a fluids and their solids. Upon applying a horizontal temperature gradient to a gallium melt alloyed with 5 weight percent indium,\\u000a the binary melt developed a vertical

J. N. Koster; R. Derebail

1997-01-01

231

Electronic behavior of calcined material obtained from a gallium-N-phenylene-N hybrid copolymer  

SciTech Connect

Calcination of a gallium-N-phenylene-N hybrid copolymer under an argon atmosphere gave nano-sized gallium nitride-carbon cluster composite material. ESR spectral examinations of the calcined materials reveals the possibility of an electron transfer in the process of gallium nitride {yields} carbon clusters with an oxidation site at gallium nitride particles and a reduction site at carbon clusters. The calcined material was found to reduce methylene blue under visible light irradiation.

Matsui, H. [Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka 577-8502 (Japan); Yamamoto, S. [Taki Chemical Co. Ltd., 64-1, Nishiwaki, Befu-cho, Kakogawa, Hyogo 675-0125 (Japan); Hama, T. [Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka 577-8502 (Japan); Karuppuchamy, S. [Molecular Engineering Institute, Kinki University, 11-6, Kayanomori, Iizuka, Fukuoka 820-8555 (Japan)], E-mail: chamy@me-henkel.fuk.kindai.ac.jp; Yoshihara, M. [Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka 577-8502 (Japan); Molecular Engineering Institute, Kinki University, 11-6, Kayanomori, Iizuka, Fukuoka 820-8555 (Japan)

2008-01-08

232

F25 IMPROVEMENTS IN XRF SPECIMEN PREPARATION USING THE DRIED RESIDUE METHOD: GALLIUM IN PLUTONIUM  

Microsoft Academic Search

The concentration of gallium in plutonium metal is critical in manufacturing nuclear weapons, and XRF is a useful method for quantifying the gallium content. A dried residue specimen preparation approach was developed recently to quantify gallium in plutonium metal.1-3 Using this method solids are analyzed, which is safer than the established process of handling radioactive aqueous solutions. The specimen preparation

Christopher G. Worley; Lisa P. Colletti

2003-01-01

233

Pure silver ohmic contacts to N- and P- type gallium arsenide materials  

DOEpatents

Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

Hogan, Stephen J. (Golden, CO) [Golden, CO

1986-01-01

234

Gallium based low-interaction anions  

DOEpatents

The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

King, Wayne A. (Santa Fe, NM); Kubas, Gregory J. (Santa Fe, NM)

2000-01-01

235

Preliminary Spectroscopic Measurements for a Gallium Electromagnetic (GEM) Thruster  

NASA Technical Reports Server (NTRS)

As a propellant option for electromagnetic thrusters, liquid ,gallium appears to have several advantages relative to other propellants. The merits of using gallium in an electromagnetic thruster (EMT) are discussed and estimates of discharge current levels and mass flow rates yielding efficient operation are given. The gallium atomic weight of 70 predicts high efficiency in the 1500-2000 s specific impulse range, making it ideal for higher-thrust, near-Earth missions. A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma and estimate electron temperature. The spectra show that neutral, singly, and doubly ionized gallium species are present in a 20 J, 1.8 kA (peak) are discharge. With graphite present on the insulator to facilitate breakdown, singly and doubly ionized carbon atoms are also present, and emission is observed from molecular carbon (CZ) radicals. A determination of the electron temperature was attempted using relative emission line data, and while the spatially and temporally averaged, spectra don't fit well to single temperatures, the data and presence of doubly ionized gallium are consistent with distributions in the 1-3 eV range.

Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

2007-01-01

236

X-ray studies of the melting and freezing phase transitions for gallium in a porous glass  

Microsoft Academic Search

We use x-ray powder diffraction to study the melting and freezing processes for gallium within a porous glass. The only modification to solid gallium was found above 20 K, in contrast with previous x-ray studies of confined gallium. The size of gallium crystallites remained nearly constant during cooling and warming, while both the melting and freezing processes were smeared. The

E. V. Charnaya; C. Tien; K. J. Lin; Yu. A. Kumzerov

1998-01-01

237

Maskless proton beam writing in gallium arsenide  

NASA Astrophysics Data System (ADS)

Proton beam writing (PBW) is a direct write technique that employs a focused MeV proton beam which is scanned in a pre-determined pattern over a target material which is subsequently electrochemically etched or chemically developed. By changing the energy of the protons the range of the protons can be changed. The ultimate depth of the structure is determined by the range of the protons in the material and this allows structures to be formed to different depths. PBW has been successfully employed on etchable glasses, polymers and semiconductor materials such as silicon (Si) and gallium arsenide (GaAs). This study reports on PBW in p-type GaAs and compares experimental results with computer simulations using the Atlassemiconductor device package from SILVACO. It has already been proven that hole transport is required for the electrochemical etching of GaAs using Tiron (4,5-dihydroxy- m-benzenedisulfonic acid, di-sodium salt). PBW in GaAs results in carrier removal in the irradiated regions and consequently minimal hole transport (in these regions) during electrochemical etching. As a result the irradiated regions are significantly more etch resistant than the non-irradiated regions. This allows high aspect ratio structures to be formed.

Mistry, P.; Gomez-Morilla, I.; Smith, R. C.; Thomson, D.; Grime, G. W.; Webb, R. P.; Gwilliam, R.; Jeynes, C.; Cansell, A.; Merchant, M.; Kirkby, K. J.

2007-07-01

238

Vertical gradient freezing of doped gallium antimonide semiconductor crystals using submerged heater growth and electromagnetic stirring  

NASA Astrophysics Data System (ADS)

An investigation of the melt growth of uniformly doped gallium-antimonide (GaSb) semiconductor crystals as well as other III-V alloy crystals with uniform composition are underway at the US Air Force Research Laboratory at Hanscom Air Force Base by the vertical gradient freeze (VGF) method utilizing a submerged heater. Stirring can be induced in the GaSb melt just above the crystal growth interface by applying a small radial electric current in the liquid together with an axial magnetic field. The transport of any dopant and/or alloy component by the stirring can promote better melt homogeneity and allow for more rapid growth rates before the onset of constitutional supercooling. This paper presents a numerical model for the unsteady transport of a dopant during the VGF process by submerged heater growth with a steady axial magnetic field and a steady radial electric current. As the strength of the electromagnetic (EM) stirring increases, the convective dopant transport increases, the dopant transport in the melt reaches a steady state at an earlier time during growth, and the top of the crystal which has solidified after a steady state has been achieved exhibits axial dopant homogeneity. For crystal growth with stronger EM stirring, the crystal exhibits less radial segregation and the axially homogeneous section of the crystal is longer. Dopant distributions in the crystal and in the melt at several different stages during growth are presented.

Ma, Nancy; Bliss, David F.; Iseler, Gerald W.

2003-11-01

239

Determination of tin, bismuth, antimony, indium, gallium and arsenic by solvent extraction cum atomic absorption spectrophotometry.  

PubMed

A rapid atomic absorption spectrometric method for the determination of tin, antimony, bismuth, indium, gallium and arsenic in geological materials, steels and alloys is described. The samples are fused with sodium peroxide (for geological samples such as cassiterite and sulphides) or decomposed with sulphuric/hydrochloric acid mixture or by alkaline fusion (for silicates or bauxites) or by acid treatment (for steels, alloys and certain geological samples). The elements of interest are extracted as their iodides into methyl isobutyl ketone, stripped into aqueous solution by treatment with benzene, concentrated nitric acid and water, and determined by flame atomic-absorption spectrometry. Detailed study is made on stripping of the metals from organic phase as there no simple and rapid stripping procedures available. The method allows the determination of Sn, Sb, Bi and In down to 2 ppm and Ga down to 5 ppm. The relative standard deviations range up to 10% with an average of 2.5%. Apparent recoveries of these metals range from 90 to 110 with an average of 95% for Sb and 99% for others. PMID:18966069

Venkaji, K; Naidu, P P; Rao, T J

1994-08-01

240

Alloy materials  

DOEpatents

An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

Hans Thieme, Cornelis Leo (Westborough, MA); Thompson, Elliott D. (Coventry, RI); Fritzemeier, Leslie G. (Acton, MA); Cameron, Robert D. (Franklin, MA); Siegal, Edward J. (Malden, MA)

2002-01-01

241

Characterization of oxygen deficient gallium oxide films grown by PLD  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy and transmission electron microscopy have been used to investigate the nature and characteristics of oxygen deficient gallium oxide films grown by pulsed laser deposition. The presence of the Ga3+ and Ga+ oxidation states, together with metallic Ga0 was observed by XPS in Ga2O2.3 sub-oxide films. TEM images reveal the presence in a Ga2O3 matrix of gallium oblong particles whose structure studied at nitrogen temperature was found to correspond to the ? monoclinic phase of metallic gallium. These results characterize the formation of nanocomposite films with Ga metallic clusters embedded in a stoichiometric Ga2O3 matrix. The nanocomposite film formation is due to a phase separation in the metastable sub-stoichiometric Ga2O2.3 film.

Petitmangin, A.; Gallas, B.; Hebert, C.; Perrière, J.; Binet, L.; Barboux, P.; Portier, X.

2013-08-01

242

The Soviet-American gallium experiment at Baksan  

SciTech Connect

A gallium solar neutrino detector is sensitive to the full range of the solar neutrino spectrum, including the low-energy neutrinos from the fundamental proton-proton fusion reaction. If neutrino oscillations in the solar interior are responsible for the suppressed {sup 8}B flux measured by the Homestake {sup 37}Cl experiment and the Kamiokande water Cherenkov detector, then a comparison of the gallium, chlorine, and water results may make possible a determination of the neutrino mass difference and mixing angle. A 30-ton gallium detector is currently operating in the Baksan laboratory in the Soviet Union, with a ratio of expected solar signal to measured background (during the first one to two {sup 71}Ge half lives) of approximately one. 28 refs.

Abazov, A. I.; Abdurashitov, D. N.; Anosov, O. L.; Danshin, S. N.; Eroshkina, L. A.; Faizov, E. L.; Gavrin, V. N.; Kalikhov, A. V.; Knodel, T. V.; Knyshenko, I. I.; Kornoukhov, V. N.; Mezentseva, S. A.; Mirmov, I. N.; Ostrinsky, A. I.; Petukhov, V. V; Pshukov, A. M.; Revzin, N. Ye; Shikhin, A. A.; Slyusareva, Ye. D.; Timofeyev, P. V.; Veretenkin, E. P.; Vermul, V. M.; Yantz, V. E.; Zakharov, Yu.; Zatsepin, G. T.; Zhandarov, V. I. [AN SSSR, Mosco

1990-01-01

243

Effect of bronchoscopy on localization of gallium-67 citrate  

SciTech Connect

Bronchoscopy, bronchoalveolar lavage (BAL), and 67Ga lung scans are frequently performed for diagnosis or follow-up of patients with sarcoidosis, interstitial pneumonitis, lymphoma, infections, and bronchogenic carcinoma. Because many patients undergo all 3 of these procedures, it is important to determine what effects bronchoscopy and/or BAL may have on gallium imaging. Because 67Ga accumulates in neutrophils at the site of an inflammatory lesion as well as in those circulating in the vascular compartment, it seems reasonable to postulate that bronchoscopy could cause migration of labeled neutrophils into the lung, resulting in false positive gallium scans. To test this hypothesis, we studied 5 patients with varying chronologic relationships of 67Ga injection, gallium scanning, and bronchoscopy with BAL. In all patients, the repeat 67Ga lung scans remained normal or showed no change after bronchoscopy and BAL. We conclude that bronchoscopy with or without BAL does not cause increased 67Ga uptake by the lung.

Phillips, B.A.; Cooper, K.R.; Fratkin, M.J.

1983-03-01

244

Dipeptide-assisted growth of uniform gallium oxohydroxide spindles  

NASA Astrophysics Data System (ADS)

The catalytic dipeptide His-Ser was used as an additive in mineralizing gallium ions to form GaOOH, a solid precursor of Ga 2O 3. This dipeptide was chosen to mimic the enzyme structure of silicatein, similar to the well-known catalytic triad of chymotrypsin. The dipeptide promoted formation of spindle-structured GaOOH under acidic conditions by behaving as a heterogeneous nucleation seed. In contrast, no well-defined, structured gallium species were produced in the absence of dipeptide. The catalytic function of the dipeptide was most pronounced at pH values in the range 3-5, which are lower than the pKa of imidazole in the His side chain. These results suggest that the catalytic role of dipeptide influences the gallium hydroxide conversion and growth. This study suggests that a designed peptide with active functionality can be further exploited to produce inorganic compounds with controlled nucleation and growth.

Lee, Inho; Kwak, Jinyoung; Haam, Seungjoo; Lee, Sang-Yup

2010-07-01

245

Gallium Phosphate Thin Films: Synthesis and Dielectric Properties  

NASA Astrophysics Data System (ADS)

Deposits of dielectric gallium phosphate thin films on silicon and gallium arsenide semiconductors have been obtained by pyrolysis of an aerosol produced by ultrasonic spraying ("pyrosol" process) and containing the organometallic precursors gallium acetylacetonate and tributyl phosphate. The composition and microstructure of the layers are discussed with respect to the experimental conditions. For this paper, electrical properties were also studied. Using the metal-insulator-semiconductor structure, the behavior of conductivity under direct current, capacitance, and dielectric loss was studied in terms of frequency, temperature, and chemical composition. The sites involved in the conduction process are structural defects directly related to the oxygen excess present in deposits which leads to the formation of M-O dangling bonds ( M=Ga or P).

Tourtin, F.; Armand, P.; Ibanez, A.; Philippot, E.

1997-11-01

246

Extremely-efficient, miniaturized, long-lived alpha-voltaic power source using liquid gallium  

NASA Technical Reports Server (NTRS)

A power source converts .alpha.-particle energy to electricity for use in electrical systems. Liquid gallium or other liquid medium is subjected to .alpha.-particle emissions. Electrons are freed by collision from neutral gallium atoms to provide gallium ions. The electrons migrate to a cathode while the gallium ions migrate to an anode. A current and/or voltage difference then arises between the cathode and anode because of the work function difference of the cathode and anode. Gallium atoms are regenerated by the receiving of electrons from the anode enabling the generation of additional electrons from additional .alpha.-particle collisions.

Snyder, G. Jeffrey (Inventor); Patel, Jagdishbhai (Inventor); Fleurial, Jean-Pierre (Inventor)

2004-01-01

247

Chemical, structural and optical studies of thermal processed gallium nitride nanoparticles  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) is one of the most promising semiconductors because of its wide direct bandgap of 3.4 eV and other unique properties, such as stability at high temperature, and ability to be alloyed with aluminum nitride and indium nitride to produce continuously tunable bandgaps from 1.9 eV to 6.2 eV. However, the photoluminescence (PL) spectrum of as-synthesized GaN usually shows a characteristic broad yellow band emission, which greatly reduces its optical output efficiency. This work focuses on identifying native defects that contribute most to the yellow band emission, and finding a processing technique to reduce these defects in GaN particles and improve the optical performance. GaN particles were heat-treated under ambient of different nitrogen sources. Chemical, structural, and optical properties of the products were characterized by various analytical techniques. Chemical analysis results show that heat-treatment of GaN under ammonia or ammonia-nitrogen mixture causes highly reactive nitrogen (N) species to react with N deficiency centers and effectively remove these states. However, X-ray diffraction (XRD), scanning electron microscopy (SEM), and PL data show that no significant structural and optical changes were observed. This proves that N deficiency is not the primary origin of the yellow band emission. When heat-treating GaN under nitrogen, oxide layers were found to be formed on the surfaces of GaN particles due to trace amounts of air leaking into the heat-treatment system. These oxide layers were examined at several stages of oxidation by microscopic, structural, and optical spectroscopic techniques. Particle morphology and nanophase characterization data show that at extensive heat-treatment times, the oxide layers formed close-packed outer shells surrounding GaN inner cores, which passivated GaN surface dangling bonds. PL spectra prove that these gallium nitride-gallium oxide core-shell structures significantly reduce the yellow band emission, thereby resulting in the strong improvement of GaN optical performance. As the GaN inner core gets sufficiently smaller, quantum confinement effect can also be observed. This suggests that the controlled surface oxidation protocol is an effective technique for fabricating GaN quantum dots from submicron-sized GaN particles.

Tong, Jing

248

Gallium-based anti-infectives: targeting microbial iron-uptake mechanisms.  

PubMed

Microbes have evolved elaborate iron-acquisition systems to sequester iron from the host environment using siderophores and heme uptake systems. Gallium(III) is structurally similar to iron(III), except that it cannot be reduced under physiological conditions, therefore gallium has the potential to serve as an iron analog, and thus an anti-microbial. Because Ga(III) can bind to virtually any complex that binds Fe(III), simple gallium salts as well as more complex siderophores and hemes are potential carriers to deliver Ga(III) to the microbes. These gallium complexes represent a new class of anti-infectives that is different in mechanism of action from conventional antibiotics. Simple gallium salts such as gallium nitrate, maltolate, and simple gallium siderophore complexes such as gallium citrate have shown good antibacterial activities. The most studied complex has been gallium citrate, which exhibits broad activity against many Gram negative bacteria at ?1-5?g/ml MICs, strong biofilm activity, low drug resistance, and efficacy in vivo. Using the structural features of specific siderophore and heme made by pathogenic bacteria and fungi, researchers have begun to evaluate new gallium complexes to target key pathogens. This review will summarize potential iron-acquisition system targets and recent research on gallium-based anti-infectives. PMID:23876838

Kelson, Andrew B; Carnevali, Maia; Truong-Le, Vu

2013-10-01

249

On-chip superconductivity via gallium overdoping of silicon  

NASA Astrophysics Data System (ADS)

We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In addition, out-of-plane critical fields of above 9 T and critical current densities exceeding 2 kA/cm2 promote these structures to be possible playgrounds for future microelectronic technology.

Skrotzki, R.; Fiedler, J.; Herrmannsdörfer, T.; Heera, V.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Helm, M.; Wosnitza, J.

2010-11-01

250

On-chip superconductivity via gallium overdoping of silicon  

SciTech Connect

We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In addition, out-of-plane critical fields of above 9 T and critical current densities exceeding 2 kA/cm{sup 2} promote these structures to be possible playgrounds for future microelectronic technology.

Skrotzki, R.; Herrmannsdoerfer, T.; Heera, V.; Voelskow, M.; Muecklich, A.; Schmidt, B.; Skorupa, W.; Helm, M.; Wosnitza, J. [Dresden High Magnetic Field Laboratory (HLD) and Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf (FZD), P.O. Box 51 01 19, D-01314 Dresden (Germany); Fiedler, J. [Dresden High Magnetic Field Laboratory (HLD) and Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf (FZD), P.O. Box 51 01 19, D-01314 Dresden (Germany); Experimental Physics, Institute of Physics, Ilmenau University of Technology, Weimarer Str. 32, 98693 Ilmenau (Germany); Gobsch, G. [Experimental Physics, Institute of Physics, Ilmenau University of Technology, Weimarer Str. 32, 98693 Ilmenau (Germany)

2010-11-08

251

First results from the Soviet-American Gallium Experiment  

SciTech Connect

The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95% CL). This is to be compared with the flux of 132 SNU predicted by the Standard Solar Model. 10 refs., 4 figs., 1 tab.

Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Eroshkina, L.A.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.I.; Petukhov, V.V.; Pshukov, A.M.; Revzin, N.Y.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zakharov, Y.; Zatsepin, G.T.; Zhandarov, V.I. (AN SSSR, Moscow (USSR). Inst. Yadernykh Issledovanij); Bowl

1990-01-01

252

Pseudomembranous colitis: a possible role for Gallium scanning  

SciTech Connect

A case of antibiotic-associated pseudomembranous colitis is presented in which the Gallium scan was the first diagnostic modality to alert the clinicians to the existence of an inflammatory bowel process. The mechanism of localization of the radiopharmaceutical in inflammatory bowel disease is discussed. Although colonoscopy is far more specific and should be the first-line diagnostic tool used in assessing the presence of pseudomembranous colitis, Gallium scanning may have a role in the follow-up of treatment and in cases of relapse.

Kramer, E.L.; Charap, M.; Sanger, J.J.; Tiu, S.S.

1983-10-01

253

Deep levels in gallium arsenide devices  

NASA Astrophysics Data System (ADS)

Deep-level traps can cause problems in gallium arsenide (GaAs) devices. Investigating deep level impurities in GaAs devices is the purpose of this research. Variable temperature current-voltage and capacitance-voltage measurements are used to characterize the devices. The devices are also investigated with deep level transient spectroscopy (DLTS) using lock-in amplifier DLTS and Fourier transform DLTS to identify the deep-level traps. The most important native defect in GaAs, EL2, is the main deep level impurity investigated and compared with the results of other researchers. Instead of a unique value of energy level and capture cross section, the deep level signature spreads over a wide range of values. Moreover, a strong correlation exists between the energy levels and the capture cross sections of the deep levels. To understand this correlation of energy level with capture cross section, a number of effects on the trap signature have been studied, including series resistance, leakage current, applied voltage (electric field), and various DLTS parameters. Numerical multiple-exponential fitting of the capacitance transients was used to extract the time constants of the transients. The measurement shows that the series resistance is not sufficiently significant to affect the DLTS result. The effects of reverse bias and filling pulse voltage appear significant in some cases. Data also show that there is an interaction between the pulse width and the window time on the correlation. The delay time during the early part of the capacitance transient in DLTS measurements can cause significant deviations of the extracted time constants. Fourier transform DLTS simulation shows that the signature of a deep level can vary significantly due to incorrect delay time consideration leading to a strong correlation between energy level and capture cross section.

Chen, Den Fu

254

Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition  

NASA Technical Reports Server (NTRS)

Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

1974-01-01

255

Gallium-Phosphide Light-Emitting Diode Array.  

National Technical Information Service (NTIS)

The goal of this program was to provide the United States Army Electronics Command with a versatile experimental display module using gallium-phosphide (GaP) light-emitting elements. The potantial advantages of a solid-state display over other presently u...

H. C. Farrell R. J. Lynch

1968-01-01

256

The 100 micron detector development program. [gallium doped germanium photoconductors  

NASA Technical Reports Server (NTRS)

An effort to optimize gallium-doped germanium photoconductors (Ge:Ga) for use in space for sensitive detection of far infrared radiation in the 100 micron region is described as well as the development of cryogenic apparatus capable of calibrating detectors under low background conditions.

Moore, W. J.

1976-01-01

257

CCMR: Bulk GaN Growth by Gallium Vapor Transport  

NSDL National Science Digital Library

Gallium nitride (GaN) is currently an extremely popular material used in the fabrication of many optoelectronic and electronic devices such as LEDs and LDs. Since gallium nitride is a direct band gap material there is a much more efficient output of energy. Unlike many other semiconductor materials such as silicon, which will emit a large portion of energy in the form of heat, gallium nitride emits mostly photons. The high electron mobility of the GaN results in the possibility of fabrication high frequency devices, high power devices which can be used for applications such as CD or DVD writing. The influence of high frequency or low wavelength lasers aids in the writing process by allowing more information to be stored in a smaller region of space. However the process required to fabricate high quality GaN crystals is still very costly and slow, thus holding industry back from fabricating mass quantities of GaN commercially. Bulk GaN Growth by Gallium Vapor Transport was attempted

Spinelli, Joseph

2005-08-17

258

URANIUM SOLUBILITY IN LIQUID GALLIUM, INDIUM, THALLIUM AND LEAD  

Microsoft Academic Search

The solubility of uranium in liquid gallium, indium, thallium, and lead ; was determined by sampling the saturated solutions. The solubilities are ; expressed by the empirical equations: in Ga (420 to 649 deg C), log (at.% U) = ; 3.571 - 3823 T⁻¹; in In (455 to 720 deg C), log (at.% U) =3.781-5146 T\\/sup -; 1\\/; in Tl

I. Johnson; M. G. Chasanov

1963-01-01

259

Results from the Soviet-American gallium experiment.  

National Technical Information Service (NTIS)

A radiochemical (sup 71)Ga-(sup 71)Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of (sup 71)Ge atoms extracted from thirty tons of gallium was measured in five runs...

A. I. Abazov O. L. Anosov E. L. Faizov V. N. Gavrin A. V. Kalikhov

1991-01-01

260

Crystallization and thermal properties of rare earth gallium garnets  

Microsoft Academic Search

The density and thermal expansion of a number of rare earth gallium garnets were studied in the liquid and solid states in the regions of crystallization and melting by irradiating the samples with a narrow beam of gamma quanta. Volume changes on liquid-solid and solid-solid transitions were measured for equilibrium and nonequilibrium crystallization. The formulas for the estimation of the

S. V. Stankus; R. A. Khairulin; P. V. Tyagel'sky; I. A. Ivanov

1995-01-01

261

Assessment of Sarcoidosis Activity by 67Gallium Lung Scan  

Microsoft Academic Search

71 consecutive patients with histologically confirmed sarcoidosis, in various clinical stages of activity, were submitted to 67Ga lung scan, and 23 of them were studied with two or more scans at intervals of 4–6 months. In patients on steroid therapy, the drug was suspended 7 days before scan to avoid the steroids interfering with the gallium (Ga) uptake mechanism. In

G. Rizzato; F. Spinelli; G. Tansini; M. Vercelloni; S. Lo Cicero; M. Mantero; L. Bertoli

1983-01-01

262

Dimerization Kinetics of Aqueous Gallium(III) Perchlorate.  

National Technical Information Service (NTIS)

Temperature jump relaxation times between 5 and 10 msec observed in pH aqueous about 0.01M gallium(III) perchlorate solutions are ascribed to the equilibrium 2 GaOH(+2)=Ga2(OH)4(+4). The first order rate constant for the rate determining step in the dimer...

E. M. Eyring J. D. Owen

1969-01-01

263

Pulmonary gallium-67 uptake in diffuse pulmonary calcinosis.  

PubMed

Diffuse pulmonary uptake of both technetium-99m- labeled methylene diphosphonate (99(m)Tc-MDP) and gallium (67Ga) citrate was noted in a patient with chronic renal failure and indicated the presence of pulmonary calcinosis. The uptake of 67Ga could be misinterpreted to represent abnormal uptake due to an opportunistic infection. PMID:8929386

Yeo, E; Miller, J H

1996-11-01

264

Pilot installation of the gallium-germanium solar neutrino telescope  

Microsoft Academic Search

The pilot gallium-germanium installation with 7 t of Ga metal is described. Preliminary results of the yields of 71Ge and 69Ge from cosmic rays are given. The possibility of conducting a calibrating experiment using a metal target and a Cr neutrino source produced from enriched chromium is considered.

I. R. Barabanov; E. P. Veretenkin; V. N. Gavrin; S. N. Danshin; L. A. Eroshkina; G. T. Zatsepin; Yu. I. Zakharov; S. A. Klimova; Yu. B. Klimov; T. V. Knodel; A. V. Kopylov; I. V. Orekhov; A. A. Tikhonov; M. I. Churmaeva

1985-01-01

265

Soviet-American gallium experiment at Baksan. A status report.  

National Technical Information Service (NTIS)

A gallium solar neutrino detector is sensitive to the full range of the solar neutrino spectrum, including the low-energy neutrinos from the fundamental proton-proton fusion reaction. If neutrino oscillations in the solar interior are responsible for the ...

A. I. Abazov D. N. Abdurashitov O. L. Anosov S. N. Danshin L. A. Eroshkina

1990-01-01

266

Pilot installation of the gallium-germanium solar neutrino telescope  

SciTech Connect

The pilot gallium-germanium installation with 7 t of Ga metal is described. Preliminary results of the yields of /sup 71/Ge and /sup 69/Ge from cosmic rays are given. The possibility of conducting a calibrating experiment using a metal target and a Cr neutrino source produced from enriched chromium is considered.

Barabanov, I.R.; Veretenkin, E.P.; Gavrin, V.N.; Danshin, S.N.; Eroshkina, L.A.; Zatsepin, G.T.; Zakharov, Y.I.; Klimova, S.A.; Klimov, Y.B.; Knodel, T.V.; and others

1985-01-25

267

Gallium nitrate ameliorates type II collagen-induced arthritis in mice.  

PubMed

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease. Gallium nitrate has been reported to reserve immunosuppressive activities. Therefore, we assessed the therapeutic effects of gallium nitrate in the mouse model of developed type II collagen-induced arthritis (CIA). CIA was induced by bovine type II collagen with Complete Freund's adjuvant. CIA mice were intraperitoneally treated from day 36 to day 49 after immunization with 3.5mg/kg/day, 7mg/kg/day gallium nitrate or vehicle. Gallium nitrate ameliorated the progression of mice with CIA. The clinical symptoms of collagen-induced arthritis did not progress after treatment with gallium nitrate. Gallium nitrate inhibited the increase of CD4(+) T cell populations (p<0.05) and also inhibited the type II collagen-specific IgG2a-isotype autoantibodies (p<0.05). Gallium nitrate reduced the serum levels of TNF-?, IL-6 and IFN-? (p<0.05) and the mRNA expression levels of these cytokine and MMPs (MMP2 and MMP9) in joint tissues. Western blotting of members of the NF-?B signaling pathway revealed that gallium nitrate inhibits the activation of NF-?B by blocking I?B degradation. These data suggest that gallium nitrate is a potential therapeutic agent for autoimmune inflammatory arthritis through its inhibition of the NF-?B pathway, and these results may help to elucidate gallium nitrate-mediated mechanisms of immunosuppression in patients with RA. PMID:24656780

Choi, Jae-Hyeog; Lee, Jong-Hwan; Roh, Kug-Hwan; Seo, Su-Kil; Choi, Il-Whan; Park, Sae-Gwang; Lim, Jun-Goo; Lee, Won-Jin; Kim, Myoung-Hun; Cho, Kwang-Rae; Kim, Young-Jae

2014-05-01

268

Pair distribution function study on compression of liquid gallium  

NASA Astrophysics Data System (ADS)

Integrating a hydrothermal diamond anvil cell (HDAC) and focused high energy x-ray beam from the superconductor wiggler X17 beamline at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL), we have successfully collected high quality total x-ray scattering data of liquid gallium. The experiments were conducted at a pressure range from 0.1GPa up to 2GPa at ambient temperature. For the first time, pair distribution functions (PDF) for liquid gallium at high pressure were derived up to 10 Å. Liquid gallium structure has been studied by x-ray absorption (Di Cicco & Filipponi, 1993; Wei et al., 2000; Comez et al., 2001), x-ray diffraction studies (Waseda & Suzuki, 1972), and molecular dynamics simulation (Tsay, 1993; Hui et al., 2002). These previous reports have focused on the 1st nearest neighbor structure, which tells us little about the atomic arrangement outside the first shell in non- crystalline materials. This study focuses on the structure of liquid gallium and the atomic structure change due to compression. The PDF results show that the observed atomic distance of the first nearest neighbor at 2.78 Å (first G(r) peak and its shoulder at the higher Q position) is consistent with previous studies by x-ray absorption (2.76 Å, Comez et al., 2001). We have also observed that the first nearest neighbor peak position did not change with pressure increasing, while the farther peaks positions in the intermediate distance range decreased with pressure increasing. This leads to a conclusion of the possible existence of "locally rigid units" in the liquid. With the addition of reverse Monte Carlo modeling, we have observed that the coordination number in the local rigit unit increases with pressure. The bulk modulus of liquid gallium derived from the volume compression curve at ambient temperature (300K) is 12.1(6) GPa.

Yu, T.; Ehm, L.; Chen, J.; Guo, Q.; Luo, S.; Parise, J.

2008-12-01

269

In vitro solubility and in vivo toxicity of gallium arsenide.  

PubMed

The in vitro solubilities of gallium arsenide (GaAs) and its metal oxides were arsenic(III) oxide greater than GaAs much greater than gallium(III) oxide. GaAs dissolution was also dependent upon the type and concentration of buffer anion. The amount of arsenic dissolved in 12 hr by various aqueous media was 0.2 M phosphate buffer greater than or equal to 0.1 M phosphate buffer greater than Krebs-Hensleit buffer greater than distilled H2O greater than HCl-KCl buffer. GaAs was apparently soluble under in vivo conditions. Blood arsenic concentrations in rats 14 days after intratracheal instillation of 10, 30, or 100 mg/kg GaAs were 5.5, 14.3, and 53.6 micrograms/ml, respectively; gallium was not detected at any doses. An increase in lung wet weight at 14 days was dose dependent with these organs retaining 17 to 42% of the dose as gallium or arsenic. Excretion of gallium and arsenic was limited to the feces. Urinary porphyrin concentrations and body weight, monitored as indices of toxicity, were significantly altered over the 14-day study. The analysis of porphyrins revealed that uroporphyrin replaced coproporphyrin as the primary urinary metabolite. Rats receiving 10, 100, or 1000 mg/kg GaAs po exhibited similar signs of toxicity. Blood arsenic concentrations at 14 days were 3.5, 6.8, and 17.6 micrograms/ml, respectively. Porphyria was increased, and body weight was decreased at 1000 mg/kg GaAs. These values were equivalent to those obtained with an intratracheal dose of 10 to 30 mg/kg GaAs. Our results showed that pulmonary and po exposure to GaAs resulted in systemic arsenic intoxication. The finding that urinary uroporphyrin concentrations were greater than coproporphyrin concentrations may serve as a sensitive indicator for GaAs exposure. PMID:6484996

Webb, D R; Sipes, I G; Carter, D E

1984-10-01

270

Pair distribution function study on compression of liquid gallium  

SciTech Connect

Integrating a hydrothermal diamond anvil cell (HDAC) and focused high energy x-ray beam from the superconductor wiggler X17 beamline at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL), we have successfully collected high quality total x-ray scattering data of liquid gallium. The experiments were conducted at a pressure range from 0.1GPa up to 2GPa at ambient temperature. For the first time, pair distribution functions (PDF) for liquid gallium at high pressure were derived up to 10 {angstrom}. Liquid gallium structure has been studied by x-ray absorption (Di Cicco & Filipponi, 1993; Wei et al., 2000; Comez et al., 2001), x-ray diffraction studies (Waseda & Suzuki, 1972), and molecular dynamics simulation (Tsay, 1993; Hui et al., 2002). These previous reports have focused on the 1st nearest neighbor structure, which tells us little about the atomic arrangement outside the first shell in non- crystalline materials. This study focuses on the structure of liquid gallium and the atomic structure change due to compression. The PDF results show that the observed atomic distance of the first nearest neighbor at 2.78 {angstrom} (first G(r) peak and its shoulder at the higher Q position) is consistent with previous studies by x-ray absorption (2.76 {angstrom}, Comez et al., 2001). We have also observed that the first nearest neighbor peak position did not change with pressure increasing, while the farther peaks positions in the intermediate distance range decreased with pressure increasing. This leads to a conclusion of the possible existence of 'locally rigid units' in the liquid. With the addition of reverse Monte Carlo modeling, we have observed that the coordination number in the local rigit unit increases with pressure. The bulk modulus of liquid gallium derived from the volume compression curve at ambient temperature (300K) is 12.1(6) GPa.

Luo, Shengnian [Los Alamos National Laboratory; Yu, Tony [SUNY-SB; Chen, Jiuhua [SUNY-SB; Ehm, Lars [SUNY-SB; Guo, Quanzhong [SUNY-SB; Parise, John [SUNY-SB

2008-01-01

271

Self- and zinc diffusion in gallium antimonide  

SciTech Connect

The technological age has in large part been driven by the applications of semiconductors, and most notably by silicon. Our lives have been thoroughly changed by devices using the broad range of semiconductor technology developed over the past forty years. Much of the technological development has its foundation in research carried out on the different semiconductors whose properties can be exploited to make transistors, lasers, and many other devices. While the technological focus has largely been on silicon, many other semiconductor systems have applications in industry and offer formidable academic challenges. Diffusion studies belong to the most basic studies in semiconductors, important from both an application as well as research standpoint. Diffusion processes govern the junctions formed for device applications. As the device dimensions are decreased and the dopant concentrations increased, keeping pace with Moore's Law, a deeper understanding of diffusion is necessary to establish and maintain the sharp dopant profiles engineered for optimal device performance. From an academic viewpoint, diffusion in semiconductors allows for the study of point defects. Very few techniques exist which allow for the extraction of as much information of their properties. This study focuses on diffusion in the semiconductor gallium antimonide (GaSb). As will become clear, this compound semiconductor proves to be a powerful one for investigating both self- and foreign atom diffusion. While the results have direct applications for work on GaSb devices, the results should also be taken in the broader context of III-V semiconductors. Results here can be compared and contrasted to results in systems such as GaAs and even GaN, indicating trends within this common group of semiconductors. The results also have direct importance for ternary and quaternary semiconductor systems used in devices such as high speed InP/GaAsSb/InP double heterojunction bipolar transistors (DHBT) [Dvorak, (2001)]. Many of the findings which will be reported here were previously published in three journal articles. Hartmut Bracht was the lead author on two articles on self-diffusion studies in GaSb [Bracht, (2001), (2000)], while this report's author was the lead author on Zn diffusion results [Nicols, (2001)]. Much of the information contained herein can be found in those articles, but a more detailed treatment is presented here.

Nicols, Samuel Piers

2002-03-26

272

Gallium-cladding compatibility testing plan. Phases 1 and 2: Test plan for gallium corrosion tests; Revision 2.  

National Technical Information Service (NTIS)

This test plan is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water-Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. The plan summarizes and updates the projected Phases 1 and 2 Gallium-Cladding compatibility co...

D. F. Wilson R. N. Morris

1998-01-01

273

Photoelectrochemical etching of gallium nitride for high quality optical devices  

NASA Astrophysics Data System (ADS)

Gallium nitride has become an important semiconductor material for a variety of device applications, including light emitting diodes (LEDs), lasers, and transistors. One of the main challenges in GaN device fabrication is the chemical stability of GaN which leads to a lack of wet etching techniques. Instead, dry etching is used almost exclusively, leading to ion damage and poor selectivity between different layers. In this dissertation, we discuss photoelectrochemical (PEC) etching, a photoassisted wet etch technique that can be used to etch GaN and its alloys. We develop new aspects of this technique to extend its applicability to a larger variety of devices and use the technique to fabricate a few optical devices, including microdisk lasers. Microdisks are circular resonant cavities that support whispering gallery modes, which propagate around the periphery of the disk, confined by total internal reflection. This geometry has been used to achieve high quality modes, small mode volume, and low threshold lasing in semiconductors such as GaAs and InGaAsP, but has been difficult to fabricate in GaN because it requires a selective wet etch to form undercut, optically isolated cavities. In this dissertation, we discuss the application of PEC etching to the fabrication of GaN microdisks. In our optically pumped, c-plane microdisks, we observe record low threshold lasing under room temperature, continuous-wave operation. In our nonpolar m-plane microdisks, we discovered that the quantum well reabsorption losses that reduce the efficiency of many GaAs and InP microdisks also limit the performance of our nonpolar microdisks, while the piezoelectric fields and corresponding Stokes shift in our c-plane microdisks lead to quantum-dot like behavior and actually lead to superior performance in the polar, c-planemicrodisks. Finally, we report of electrically driven operation of c-plane microdisks for the first time. In these microdisks, first order whispering gallery modes are observed under both optical and electrical injection. We also examine new applications of PEC etching in this dissertation. We have discovered that m-plane GaN, grown homoepitaxially on bulk GaN substrates, etches much more smoothly and predictably than c-plane GaN on sapphire because of the lower defect density and reduced chemical stability of the nonpolar facets. We are able to obtain highly bandgap-selective top-down etching, deep, anisotropic etching, and etches with angled facets. These etch studies open up the possibility of a variety of new m-plane devices fabricated with PEC etching, such as chip-shaped LEDs. We also develop a method for PEC etching of p-type GaN, which has been very difficult to achieve in any semiconductor system. We apply this technique to surface roughening of the p-type, Ga-face side of c-plane LEDs, increasing the light extraction efficiency without the need for flip-chip bonding or substrate removal.

Tamboli, Adele C.

274

Iridium alloy  

US Patent & Trademark Office Database

An iridium alloy consists essentially of iridium and at least one of W and Zr, and optionally Rh. When present, W comprises between 0.01 and 5 wt % of the alloy; when present in combination with W, Zr comprises between 0.01 and 0.5 wt % of the alloy; when present alone or in combination with Rh only, Zr comprises between 0.01 and 0.09 wt % of the alloy; and when present, Rh comprises between 0.1 and 5 wt % of the alloy. The alloys may be modified by the addition of platinum and other platinum group metals and base metals. The alloys demonstrate enhanced physical and chemical properties and are suitable for use as electrode materials in spark plugs and other high temperature applications.

2009-01-27

275

Gallium uptake in the thyroid gland in amiodarone-induced hyperthyroidism  

SciTech Connect

Amiodarone is an iodinated antiarrhythmic agent that is effective in the treatment of atrial and ventricular arrhythmias. A number of side effects are seen, including pulmonary toxicity and thyroid dysfunction. A patient with both amiodarone-induced pneumonitis and hyperthyroidism who exhibited abnormal gallium activity in the lungs, as well as diffuse gallium uptake in the thyroid gland is presented. The latter has not been previously reported and supports the concept of iodide-induced thyroiditis with gallium uptake reflecting the inflammatory response.

Ling, M.C.; Dake, M.D.; Okerlund, M.D.

1988-04-01

276

CD71 phenotype and the value of gallium imaging in lymphomas  

SciTech Connect

Tumor cells of 14 cases of non-Hodgkin lymphomas and 2 cases of Hodgkin disease were tested for the presence of the transferrin receptor (CD71) by flow cytofluorimetry before 67gallium imaging. It appeared that expression of CD71 phenotype was closely related to the positivity of gallium scan before therapy. We feel that this test is able to predict the avidity for 67gallium and the clinical implications are discussed.

Feremans, W.; Bujan, W.; Neve, P.; Delville, J.P.; Schandene, L. (Cliniques Universitaires de Bruxelles, Hopital Erasme (Belgium))

1991-03-01

277

Cutaneous gallium uptake in patients with AIDS with mycobacterium avium-intracellulare septicemia  

SciTech Connect

Gallium imaging is increasingly being used for the early detection of complications in patients with AIDS. A 26-year-old homosexual man who was HIV antibody positive underwent gallium imaging for investigation of possible Pneumocystis carinii pneumonia. Widespread cutaneous focal uptake was seen, which was subsequently shown to be due to mycobacterium avium-intracellulare (MAI) septicemia. This case demonstrates the importance of whole body imaging rather than imaging target areas only, the utility of gallium imaging in aiding the early detection of clinically unsuspected disease, and shows a new pattern of gallium uptake in disseminated MAI infection.

Allwright, S.J.; Chapman, P.R.; Antico, V.F.; Gruenewald, S.M.

1988-07-01

278

Gallium-Cooled Target for Compact Accelerator-Based Neutron Sources  

NASA Astrophysics Data System (ADS)

This paper discusses the motivation for gallium cooling of targets of compact accelerator-based neutron sources (CANS); summarizes features of the low-power alternative, i.e., water cooling, and the limitations of boiling water heat transfer; lists the properties of liquid gallium; and cites its low hazards potential. I set out working equations for heat transport and fluid flow in liquid gallium and present a concept for a gallium-cooled system, including a scoping calculation of temperatures and pressure drops, and present conclusions and a recommendation.

Carpenter, John M.

279

Vapor-phase epitaxy of gallium nitride by gallium arc discharge evaporation  

NASA Astrophysics Data System (ADS)

Vapor-phase epitaxy of GaN was performed by combining ammonia with gallium evaporated into an inert gas stream by a DC arc discharge, and letting the mixture pass through a pair of heated graphite susceptors. Growth rates as high as 30 ?m/h were achieved. The growth on the top sample was specular in a large area, and was of high quality as characterized by atomic force microscopy and photoluminescence spectroscopy. The bottom sample had a high density of macroscopic defects, presumably caused by Ga droplets in the gas phase resulting from the arc evaporation process. The experimental growth rate was found to be less than {1}/{3} of values predicted in a computer flow dynamic model of the growth system, and Ga-NH 3 pre-reactions were implicated as the likely cause of the discrepancy. The growth efficiency, calculated to 2%, could arguably be improved by reducing the reactor growth pressure, and by changing the reactor geometry to avoid Ga condensation on walls. Potential advantages of the described growth technique are cheap source materials of high purity and low equipment costs. Furthermore, since no corrosive gasses were used, hardware corrosion and gas-phase impurities can be reduced.

Heikman, S.; Keller, S.; Mishra, U. K.

2006-08-01

280

Zinc diffusion in gallium arsenide and the properties of gallium interstitials  

NASA Astrophysics Data System (ADS)

We have performed zinc diffusion experiments in gallium arsenide at temperatures between 620°C and 870°C with a dilute Ga-Zn source. The low Zn partial pressure established during annealing realizes Zn surface concentrations of ?2×1019cm-3 , which lead to the formation of characteristic S-shaped diffusion profiles. Accurate modeling of the Zn profiles, which were measured by means of secondary ion mass spectroscopy, shows that Zn diffusion under the particular doping conditions is mainly mediated by neutral and singly positively charged Ga interstitials via the kick-out mechanism. We determined the temperature dependence of the individual contributions of neutral and positively charged Ga interstitials to Ga diffusion for electronically intrinsic conditions. The data are lower than the total Ga self-diffusion coefficient and hence consistent with the general interpretation that Ga diffusion under intrinsic conditions is mainly mediated by Ga vacancies. Our results disprove the general accepted interpretation of Zn diffusion in GaAs via doubly and triply positively charged Ga interstitials and solves the inconsistency related to the electrical compensation of the acceptor dopant Zn by the multiply charged Ga interstitials.

Bracht, H.; Brotzmann, S.

2005-03-01

281

Critical Fields and Growth Rates of the Tayler Instability as Probed by a Columnar Gallium Experiment  

NASA Astrophysics Data System (ADS)

Many astrophysical phenomena (such as the slow rotation of neutron stars or the rigid rotation of the solar core) can be explained by the action of the Tayler instability of toroidal magnetic fields in the radiative zones of stars. In order to place the theory of this instability on a safe fundament, it has been realized in a laboratory experiment measuring the critical field strength, the growth rates, as well as the shape of the supercritical modes. A strong electrical current flows through a liquid metal confined in a resting columnar container with an insulating outer cylinder. As the very small magnetic Prandtl number of the gallium-indium-tin alloy does not influence the critical Hartmann number of the field amplitudes, the electric currents for marginal instability can also be computed with direct numerical simulations. The results of this theoretical concept are confirmed by the experiment. Also the predicted growth rates on the order of minutes for the nonaxisymmetric perturbations are certified by the measurements. That they do not directly depend on the size of the experiment is shown as a consequence of the weakness of the applied fields and the absence of rotation.

Rüdiger, Günther; Gellert, Marcus; Schultz, Manfred; Strassmeier, Klaus G.; Stefani, Frank; Gundrum, Thomas; Seilmayer, Martin; Gerbeth, Gunter

2012-08-01

282

Raman spectroscopy study of wurtzite crystals: Gallium nitride and zinc oxide  

NASA Astrophysics Data System (ADS)

Raman spectroscopic techniques have been used to study wurtzite crystals gallium nitride (GaN) and zinc oxide (ZnO). These semiconductors have attracted considerable interest in the past few years for their applications in optoelectronics and high-temperature microelectronics. The sensitivity of Raman spectroscopy to lattice strain and doping have motivated several studies of these materials, particularly GaN and its alloys with indium nitride and aluminum nitride. However, results from different authors are inconsistent, and the theoretical interpretation of the data is questionable. Much of the experimental work discussed in this dissertation was performed with a special high-resolution Raman instrument that makes it possible to obtain accurate line shapes and peak positions. This capability, combined with a theoretical analysis that takes into account the special symmetry properties of wurtzite crystals and utilizes results from state-of-the-art ab initio calculations, has lead to a much better understanding of lattice dynamics in GaN and ZnO and to the resolution of many of the puzzles in the literature. Highlights of the work presented here are the explanation of the anomalously large linewidth of the A1 longitudinal optical phonon in GaN, the discovery and explanation of dispersive effects in the phonon self-energy in GaN and ZnO and a critical study of the reliability of Raman spectroscopy for the determination of doping levels and mobilities in GaN films.

Shi, Lingyun

283

Vapor-Phase Synthesis of Gallium Phosphide Nanowires  

SciTech Connect

Gallium phosphide (GaP) nanowires were synthesized in a high yield by vapor-phase reaction of gallium vapor and phosphorus vapor at 1150 C in a tube furnace system. The nanowires have diameters in the range of 25-100 nm and lengths of up to tens of micrometers. Twinning growth occurs in GaP nanowires, and as a result most nanowires contain a high density of twinning faults. Novel necklacelike GaP nanostructures that were formed by stringing tens of amorphous Ga-P-O microbeads upon one crystalline GaP nanowires were also found in some synthesis runs. This simple vapor-phase approach may be applied to synthesize other important group III-V compound nanowires.

Gu, Dr Zhanjun [University of Georgia, Athens, GA; Paranthaman, Mariappan Parans [ORNL; Pan, Zhengwei [University of Georgia, Athens, GA

2009-01-01

284

Gallium nitride nanowires by maskless hot phosphoric wet etching  

NASA Astrophysics Data System (ADS)

We demonstrate gallium nitride (GaN) nanowires formation by controlling the selective and anisotropic etching of N-polar GaN in hot phosphoric acid. Nanowires of ~109/cm,2 total height of ~400 nm, and diameters of 170-200 nm were obtained. These nanowires have both non-polar {1100}/ {1120} and semi-polar {1011} facets. X-Ray Diffraction characterization shows that screw dislocations are primarily responsible for preferential etching to create nanowires. Indium gallium nitride multi-quantum wells (MQWs) grown on these GaN nanowires showed a blue shift in peak emission wavelength of photoluminescence spectra, and full width at half maximum decreased relative to MQWs grown on planar N-polar GaN, respectively.

Bharrat, D.; Hosalli, A. M.; Van Den Broeck, D. M.; Samberg, J. P.; Bedair, S. M.; El-Masry, N. A.

2013-08-01

285

Electronic effects on the melting of small gallium clusters  

NASA Astrophysics Data System (ADS)

Motivated by experimental reports of higher-than-bulk melting temperatures in small gallium clusters, we perform first-principles molecular dynamics simulations of Ga20 and Ga20+ using parallel tempering in the microcanonical ensemble. The respective specific heat (CV) curves, obtained using the multiple histogram method, exhibit a broad peak centered at approximately 740 and 610 K--well above the melting temperature of bulk gallium (303 K) and in reasonable agreement with experimental data for Ga20+. Assessment of atomic mobility confirms the transition from solid-like to liquid-like states near the CV peak temperature. Parallel tempering molecular dynamics simulations yield low-energy isomers that are ~0.1 eV lower in energy than previously reported ground state structures, indicative of an energy landscape with multiple, competing low-energy morphologies. Electronic structure analysis shows no evidence of covalent bonding, yet both the neutral and charged clusters exhibit greater-than-bulk melting temperatures.

Steenbergen, K. G.; Schebarchov, D.; Gaston, N.

2012-10-01

286

Deep ultraviolet enhanced wet chemical etching of gallium nitride  

NASA Astrophysics Data System (ADS)

We report a study of the ultraviolet (UV) irradiation effects on the wet chemical etching of unintentionally doped n-type gallium nitride (GaN) layers grown on sapphire substrates. When illuminated with a 253.7 nm mercury line source, etching of GaN is found to take place in aqueous phosphorus acid (H3PO4) and potassium hydroxide (KOH) solutions of pH values ranging from -1 to 2 and 11 to 15, respectively. Formation of gallium oxide is observed on GaN when illuminated in dilute H3PO4 and KOH solutions. These results are attributed to a two-step reaction process upon which the UV irradiation is shown to enhance the oxidative dissolution of GaN.

Peng, L.-H.; Chuang, C.-W.; Ho, J.-K.; Huang, C.-N.; Chen, C.-Y.

1998-02-01

287

Preparation Of Copper Indium Gallium Diselenide Films For Solar Cells  

DOEpatents

High quality thin films of copper-indium-gallium-diselenide useful in the production of solar cells are prepared by electrodepositing at least one of the constituent metals onto a glass/Mo substrate, followed by physical vapor deposition of copper and selenium or indium and selenium to adjust the final stoichiometry of the thin film to approximately Cu(In,Ga)Se.sub.2. Using an AC voltage of 1-100 KHz in combination with a DC voltage for electrodeposition improves the morphology and growth rate of the deposited thin film. An electrodeposition solution comprising at least in part an organic solvent may be used in conjunction with an increased cathodic potential to increase the gallium content of the electrodeposited thin film.

Bhattacharya, Raghu N. (Littleton, CO); Contreras, Miguel A. (Golden, CO); Keane, James (Lakewood, CO); Tennant, Andrew L. (Denver, CO), Tuttle, John R. (Denver, CO); Ramanathan, Kannan (Lakewood, CO); Noufi, Rommel (Golden, CO)

1998-08-08

288

Results from the Soviet-American gallium experiment  

SciTech Connect

A radiochemical [sup 7l]Ga--[sup 7l]Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of [sup 7l]Ge atoms extracted from 30 tons of gallium in 1990 and 57 tons in 1991 was measured in twelve runs during the period of January 1990 to December 1991. For the 1990 data, we observed the capture rate to be 20 + 15/[minus]20 (stat) [plus minus]32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model. The 1991 data, taken with 57 tons of gallium, shows a non zero [sup 7l]Ge signal. A final result from the 1990 and 1991 data is still pending completion of studies of possible systematic effects.

Anosov, O.L.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mirmov, I.N.; Ostrinsky, A.V.; Pshukov, A.M.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zatsepin, G.T. (AN SSSR, Moscow (Russian Federation). Inst. Yadernykh Issledovanij); Bowles, T.J.; Elliott, S.R.; Nico, J.S.; O'Brien, H.A.; Wark, D.L.; Wilkerson, J.F. (Los Alamos National Lab., NM (U

1992-01-01

289

Corrosion of alloy 718 in a mercury thermal convection loop  

SciTech Connect

Two thermal convection loops (TCLs) fabricated from annealed alloy 718 continuously circulated mercury (Hg) with 1000 wppm gallium (Ga), respectively, for about 5000 h, duplicating previous TCL tests for annealed 316L. In each case, the maximum loop temperature was 305C, the minimum temperature was 242C, and the Hg flow rate was approximately 1.2 m/min. Unlike the 316L exposed to Hg, which above about 260C exhibited a thin, porous surface layer depleted in Ni and Cr, the alloy 718 coupons revealed essentially no wetting and, therefore, no interaction with that Hg at any temperature. Alloy 718 coupons suspended in the loops revealed inconsequentially small weight changes, and both the coupons and loop tubing exhibited no detectable metallographic evidence of attack.

Pawel, S.J.; DiStefano, J.R.; Manneschmidt, E.T.

1999-12-01

290

Atomic Mass and Nuclear Binding Energy for Ga-67 (Gallium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume A `Nuclei with Z = 1 - 54' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Ga-67 (Gallium, atomic number Z = 31, mass number A = 67).

Sukhoruchkin, S. I.; Soroko, Z. N.

291

Lattice constants, thermal expansion and compressibility of gallium nitride  

Microsoft Academic Search

High-resolution X-ray diffraction measurements can be performed at variable temperatures and pressures. The usefulness of such experiments is shown when taking gallium nitride, which is a wide-band semiconductor, as an example. The GaN samples were grown at high pressures (bulk crystals) and as epitaxial layers on silicon carbide and sapphire. The X-ray examinations were done at temperatures of 293-750 K

M. Leszczynski; T. Suski; P. Perlin; H. Teisseyre; I. Grzegory; M. Bockowski; J. Jun; S. Porowski; Major J

1995-01-01

292

TUNABLE TERAHERTZ GENERATION IN QUASI-PHASEMATCHED GALLIUM ARSENIDE  

Microsoft Academic Search

Sources of electromagnetic radiation with terahertz (THz) frequencies have been actively investigated during the last decade for applications in imaging and spectroscopic sensors. Femtosecond optical pulses have been shown to efficiently generate THz waves in quasi-phasematched (QPM) gallium arsenide (GaAs) (1). In this work we demonstrate a picosecond system creating a near diffraction-limited THz source with 1 mW of average

Joseph E. Schaar; Konstantin L. Vodopyanov; Martin M. Fejer

293

Terahertz Cherenkov radiation from ultrafast magnetization in terbium gallium garnet  

NASA Astrophysics Data System (ADS)

We report an experimental observation of terahertz Cherenkov radiation from a moving magnetic moment produced in terbium gallium garnet by a circularly polarized femtosecond laser pulse via the inverse Faraday effect. Contrary to some existing theoretical predictions, the polarity of the observed radiation unambiguously demonstrates the paramagnetic, rather than diamagnetic, nature of the ultrafast inverse Faraday effect. From measurements of the radiation field, the Verdet constant in the subpicosecond regime is ˜3-10 times smaller than its table quasistatic value.

Gorelov, S. D.; Mashkovich, E. A.; Tsarev, M. V.; Bakunov, M. I.

2013-12-01

294

The Russian-American Gallium solar neutrino Experiment  

SciTech Connect

The Russian-American Gallium solar neutrino Experiment (SAGE) is described. The solar neutrino flux measured by 31 extractions through October, 1993 is presented. The result of 69 {+-} 10{sub {minus}7}{sup +5} SNU is to be compared with a standard solar model prediction of 132 SNU. The status of a {sup 51}Cr neutrino source irradiation to test the overall operation of the experiment is also presented.

Elliott, S.R. [Univ. of Washington, Seattle, WA (United States); Abdurashitov, J.N. [Russian Academy of Sciences, Moscow (Russian Federation). Inst. for Nuclear Research; Bowles, T.J. [Los Alamos National Lab., NM (United States)] [and others

1995-12-31

295

The Russian-American gallium solar neutrino experiment  

SciTech Connect

The Russian-American Gallium solar neutrino Experiment (SAGE) is described. The solar neutrino flux measured by 31 extractions through October, 1993 is presented. The result of 69 {+-} 10{sub {minus}7}{sup +5} SNU is to be compared with a standard solar model prediction of 132 SNU. The status of a {sup 51}Cr neutrino source irradiation to test the overall operation of the experiment is also presented.

Elliott, S.R.; Wilkerson, J.F. [Univ. of Washington, Seattle, WA (United States); Abdurashitov, J.N. [Russian Academy of Sciences, Moscow (Russian Federation). Institute of Nuclear Research] [and others

1995-08-01

296

Bulk Zinc Oxide and Gallium Nitride Crystals by Solvothermal Techniques  

Microsoft Academic Search

We report on recent achievements from the growth of hydrothermal zinc oxide (ZnO) and ammonothermal gallium nitride (GaN).\\u000a A thin-film deposition technique under conditions near the thermodynamic equilibrium, liquid phase epitaxy (LPE) is applied\\u000a for fast screening of dopants and their effects on physical properties of ZnO. In particular, super fast luminescent decay\\u000a will be reported from some donor-acceptor co-doped

D. Ehrentraut; T. Fukuda

297

Indium, tin, and gallium doped cadmium selenide quantum dots  

NASA Astrophysics Data System (ADS)

Doping quantum dots to increase conductivity is a crucial step towards being able to fabricate a new generation of electronic devices built on the "bottom-up" platform that are smaller and more efficient than currently available. Indium, tin, and gallium have been used to dope CdSe in both the bulk and thin film regimes and introduce n-type electron donation to the conduction band. CdSe quantum dots have been successfully doped with indium, tin, and gallium using the Li4[Cd10Se4 (SPh16)] single source precursor combined with metal chloride compounds. Doping CdSe quantum dots is shown to effect particle growth dynamics in the "heterogeneous growth regime." Doping with indium, tin, and gallium introduce donor levels 280, 100, and 50 meV below the conduction band minimum, respectively. Thin films of indium and tin doped quantum dots show improved conductivity over films of undoped quantum dots. Transient Absorption spectroscopy indicates that indium doping introduces a new electron energy level in the conduction band that results in a 70 meV blue shift in the 1Se absorption bleach position. Novel characterization methods such as in-situ fluorescence growth monitoring, single quantum dot EDS acquisition, static and time-resolved temperature dependant fluorescence spectroscopy were developed in the course of this work as well. These results show that doping CdSe quantum dots with indium, tin, and gallium has not only been successful but has introduced new electronic properties to the quantum dots that make them superior to traditional CdSe quantum dots.

Tuinenga, Christopher J.

298

Design, fabrication, and characterization of gallium nitride high power rectifiers  

Microsoft Academic Search

The edge termination design, device modeling, fabrication and characterization of gallium nitride (GaN) high power diode rectifiers are reported in this dissertation. The important parameter sets of GaN materials and physical models are first reviewed and applied to the standard drift-diffusion device simulator MEDICI(TM). Theoretical calculations of GaN high power rectifiers have been made based on the breakdown voltage, the

Kwang Hyeon Baik

2004-01-01

299

POLLUTION PREVENTION IN THE SEMICONDUCTOR INDUSTRY THROUGH RECOVERY AND RECYCLING OF GALLIUM AND ARSENIC FROM GAAS POLISHING WASTES  

EPA Science Inventory

A process was developed for the recovery of both arsenic and gallium from gallium arsenide polishing wastes. The economics associated with the current disposal techniques utilizing ferric hydroxide precipitation dictate that sequential recovery of toxic arsenic and valuble galliu...

300

Appraisal of lupus nephritis by renal imaging with gallium-67  

SciTech Connect

To assess the activity of lupus nephritis, 43 patients with systemic lupus erythematosus (SLE) were studied by gallium imaging. Delayed renal visualization 48 hours after the gallium injection, a positive result, was noted in 25 of 48 scans. Active renal disease was defined by the presence of hematuria, pyuria (10 or more red blood cells or white blood cells per high-power field), proteinuria (1 g or more per 24 hours), a rising serum creatinine level, or a recent biopsy specimen showing proliferative and/or necrotizing lesions involving more than 20 percent of glomeruli. Renal disease was active in 18 instances, inactive in 23, and undetermined in seven (a total of 48 scans). Sixteen of the 18 scans (89 percent) in patients with active renal disease showed positive findings, as compared with only four of 23 scans (17 percent) in patients with inactive renal disease (p less than 0.001). Patients with positive scanning results had a higher rate of hypertension (p = 0.02), nephrotic proteinuria (p = 0.01), and progressive renal failure (p = 0.02). Mild mesangial nephritis (World Health Organization classes I and II) was noted only in the patients with negative scanning results (p = 0.02) who, however, showed a higher incidence of severe extrarenal SLE (p = 0.04). It is concluded that gallium imaging is a useful tool in evaluating the activity of lupus nephritis.

Bakir, A.A.; Lopez-Majano, V.; Hryhorczuk, D.O.; Rhee, H.L.; Dunea, G.

1985-08-01

301

Radioscopic visualization of isothermal solidification of eutectic Ga-ln alloy  

Microsoft Academic Search

The phase diagram for a gallium-indium alloy shows that the eutectic is formed at a temperature of 15.3 C and has a eutectic composition of 14.2 at. pct In (21.4 wt pct In). A eutectic melt is expected to solidify completely when the eutectic temperature is reached. This requires that no gravitational segregation occurs in the melt. A survey of

R. Derebail; J. N. Koster

1996-01-01

302

Heusler alloys  

Microsoft Academic Search

In 1903 F. Heusler reported that it was possible to make ferromagnetic alloys from non-ferromagnetic constituents copper-manganese bronze and group B elements such as aluminium and tin. Further investigations showed that the magnetic properties of these alloys are related to their chemical, L21, structure, and to the ordering of the manganese atoms on an f.c.c. sublattice.Heusler alloys are properly described

Peter J. Webster

1969-01-01

303

Generalized stacking fault energies of alloys  

NASA Astrophysics Data System (ADS)

The generalized stacking fault energy (? surface) provides fundamental physics for understanding the plastic deformation mechanisms. Using the ab initio exact muffin-tin orbitals method in combination with the coherent potential approximation, we calculate the ? surface for the disordered Cu–Al, Cu–Zn, Cu–Ga, Cu–Ni, Pd–Ag and Pd–Au alloys. Studying the effect of segregation of the solute to the stacking fault planes shows that only the local chemical composition affects the ? surface. The calculated alloying trends are discussed using the electronic band structure of the base and distorted alloys. Based on our ? surface results, we demonstrate that the previous revealed ‘universal scaling law’ between the intrinsic energy barriers (IEBs) is well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning measure parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability.

Li, Wei; Lu, Song; Hu, Qing-Miao; Kwon, Se Kyun; Johansson, Börje; Vitos, Levente

2014-07-01

304

Generalized stacking fault energies of alloys.  

PubMed

The generalized stacking fault energy (? surface) provides fundamental physics for understanding the plastic deformation mechanisms. Using the ab initio exact muffin-tin orbitals method in combination with the coherent potential approximation, we calculate the ? surface for the disordered Cu-Al, Cu-Zn, Cu-Ga, Cu-Ni, Pd-Ag and Pd-Au alloys. Studying the effect of segregation of the solute to the stacking fault planes shows that only the local chemical composition affects the ? surface. The calculated alloying trends are discussed using the electronic band structure of the base and distorted alloys.Based on our ? surface results, we demonstrate that the previous revealed 'universal scaling law' between the intrinsic energy barriers (IEBs) is well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning measure parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability. PMID:24903220

Li, Wei; Lu, Song; Hu, Qing-Miao; Kwon, Se Kyun; Johansson, Börje; Vitos, Levente

2014-07-01

305

Zintl cluster chemistry in the alkali-metal-gallium systems  

SciTech Connect

Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs{sub 8}Ga{sub 11}. The geometry of the Ga{sub 11}{sup 7{minus}} unit is not deltahedral but can be described as a penta-capped trigonal prism. The reduction of the charge from a closo-Ga{sub 11}{sup 13{minus}} to Ga{sub 11}{sup 7{minus}} is believed to be the driving force of the distortion. The compound is paramagnetic because of an extra electron but incorporation of a halide atom into the structure captures the unpaired electron and forms a diamagnetic compound. A second isolated cluster has been found in Na{sub 10}Ga{sub 10}Ni where the tetra-capped trigonal prismatic gallium is centered by nickel. Stabilization of the cluster occurs through Ni-Ga bonding. A simple two-dimensional network occurs in the binary K{sub 2}Ga{sub 3} Octahedra are connected through four waist atoms to form a layered structure with the potassium atoms sitting between the layers. Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x} is nonstoichiometric and needs only a small amount of silver to form (x {approximately} 2--6). The structure is composed of three different clusters which are interconnected to form a three-dimensional structure. The RbGa{sub 3{minus}x}Au{sub x} system is also nonstoichiometric with a three-dimensional structure composed of Ga{sub 8} dodecahedra and four-bonded gallium atoms. Unlike Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x}, the RbGa{sub 3} binary is also stable. The binary is formally a Zintl phase but the ternary is not. Some chemistry in the alkali-metal-indium system also has been explored. A new potassium-indium binary is discussed but the structure has not been completely characterized.

Henning, R.

1998-03-27

306

Spintronics: Towards room temperature ferromagnetic devices via manganese and rare earth doped gallium nitride  

NASA Astrophysics Data System (ADS)

Spintronics is a multidisciplinary field aimed at the active manipulation of spin degrees of freedom in solid-state systems. The goal being the understanding of the interaction between the particle spin and its solid-state environment, and the making of useful devices based on the acquired knowledge. If Moore's law is to continue, then we need to find alternatives to conventional microelectronics. Where conventional electronic devices rely on manipulating charge to produce desired functions, spintronic devices would manipulate both the charge flow and electron spin within that flow. This would add an extra degree of freedom to microelectronics and usher in the era of truly nanoelectronic devices. Research aimed at a whole new generation of electronic devices is underway by introducing electron spin as a new or additional physical variable, and semiconductor devices that exploit this new freedom will operate faster and more efficiently than conventional microelectronic devices and offer new functionality that promises to revolutionize the electronics industry. Long recognized as the material of choice for next-generation solid-state lighting, gallium nitride (GaN) also has proven uses in the field of high power, high frequency field-effect transistors (FETs). But its promise as a material system for spintronic applications may be its ultimate legacy. In this dissertation, the growth of gallium-manganese-nitride (GaMnN) compound semiconductor alloy was investigated through the use of an in-house built metal-organic chemical vapor deposition (MOCVD) reactor. Building on previous investigations of ferromagnetic mechanisms in GaMnN, where ferromagnetism was shown to be carrier mediated, a above room temperature ferromagnetic GaMnN i-p-n diode structure was conceived. This device proved to be the first of its kind in the world, where ferromagnetic properties are controlled via proximity of the mediating holes, upon voltage bias of adjacent structure layers. Simultaneously, post-growth diffusion of ferromagnetic, rare earth species into GaN template thin films also was investigated. Structural, electrical, optical and magnetic characterization of diffused films grown on sapphire was performed. Optimization of the conditions leading to the first successful diffusion of neodymium into GaN thin films, and the magnetic and optical studies that followed are detailed. A mechanism governing and conditions promoting ferromagnetism in rare earth (RE) doped GaN is proposed. The magnetic relationship between two similar and dissimilar rare earth elements, in a single GaN crystal are investigated. Finally, spin valve and magnetic tunnel junction devices based on the magnetic properties of RE-GaN thin films are investigated.

Luen, Melvyn Oliver

307

Synthesis and use of (polyfluoroaryl)fluoroanions of aluminum, gallium and indium  

DOEpatents

Salts of (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are described. The (polyfluoroaryl)fluoroanions have the formula [ER'R"R'"F].sup..crclbar. wherein E is aluminum, gallium, or indium, wherein F is fluorine, and wherein R', R", and R'" is each a fluorinated phenyl, fluorinated biphenyl, or fluorinated polycyclic group.

Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Midland, MI)

2000-01-01

308

Low temperature recombination and trapping analysis in high purity gallium arsenide by microwave photodielectric techniques  

NASA Technical Reports Server (NTRS)

Some physical theories pertinent to the measurement properties of gallium arsenide are presented and experimental data are analyzed. A model for explaining recombination and trapping high purity gallium arsenide, valid below 77 K is assembled from points made at various places and an appraisal is given of photodielectric techniques for material property studies.

Khambaty, M. B.; Hartwig, W. H.

1972-01-01

309

NOTE ON A REDETERMINATION OF THE ALUMINIUM-GALLIUM EQUILIBRIUM DIAGRAM  

Microsoft Academic Search

Thermal analysis was used to establish the form of the aluminum -- ; gallium equilibrium diagram. The system was found to consist of a simple ; eutectic with a eutectic temperature of 26.6 deg C; the eutectic composition was ; not established. Metalographic and x-ray examination confirmed the existence of ; only two phases--aluminum and gallium. A tentative solidus was

1958-01-01

310

Clinical value of gallium-67 scintigraphy in assessment of disease activity in Wegener's granulomatosis  

PubMed Central

Background: Diagnosis of active pulmonary and paranasal involvement in patients with Wegener's granulomatosis (WG) can be difficult. The diagnostic value of gallium-67 scintigraphy in WG is unclear. Objective: To evaluate the added diagnostic value of gallium-67 scintigraphy in patients with WG with suspected granulomatous inflammation in the paranasal and chest regions. Methods: Retrospectively, the diagnostic contribution of chest and head planar gallium scans in 40 episodes of suspected vasculitis disease activity in 28 patients with WG was evaluated. Scans were grouped into normal or increased uptake for each region. Histological proof or response to treatment was the "gold standard" for the presence of WG activity. Results: WG activity was confirmed in 8 (20%) episodes, with pulmonary locations in three, paranasal in four, and both in one (n=7 patients); all these gallium scans showed increased gallium uptake (sensitivity 100%). Gallium scans were negative for the pulmonary area in 23/36 scans (specificity 64%), and negative for paranasal activity in 13/16 scans (specificity 81%) in episodes without WG activity. Positive predictive value of WG activity for lungs and paranasal region was 24% and 63%, respectively, negative predictive value was 100% for both regions. False positive findings were caused by bacterial or viral infections. Conclusion: Gallium scans are clinically helpful as a negative scan virtually excludes active WG. Gallium scintigraphy of chest and nasal region has a high sensitivity for the detection of disease activity in WG. However, because of positive scans in cases of bacterial or viral infections, specificity was lower.

Slart, R; Jager, P; Poot, L; Piers, D; Cohen, T; Stegeman, C

2003-01-01

311

Gallium-67 citrate localization in the heart secondary to constrictive pericarditis with myocardial fibrosis  

SciTech Connect

Scintigraphy has demonstrated gallium-67 accumulation within the heart in pericarditis and cardiomopathies of various kinds. A case report is presented of a 63-yr-old man with multisystem disease who showed extensive myocardial uptake of Ga-67 by scintigraphy. At autopsy, constrictive pericarditis with myocardial fibrosis was found. Gallium-67 localzation has not been documented previously in myocarial fibrosis accompanying constrictive pericarditis.

Moreno, A.J.; Brown, J.M.; Spicer, M.J.; Mena, H.; Brown, T.J.

1984-01-01

312

Determination of gallium concentration in blood-free tissues using a radiolabeled blood marker  

Microsoft Academic Search

Radioiodinated serum albumin has been used as a blood marker to define and quantitate physiological volumes for 12 organs and tissue types. The concentration of gallium-67 in blood-free tissues of rats was also determined at various times after intravenous administration. Tissues were divided into two kinetically distinguishable types based on reported nonuniform distribution of the blood marker and the gallium

J. W. Triplett; T. L. Hayden; L. K. McWhorter; S. R. Gautam; E. E. Kim; D. W. A. Bourne

1985-01-01

313

The distribution of nickel, cobalt, gallium, palladium and gold in iron meteorites  

Microsoft Academic Search

The concentrations of nickel, cobalt, gallium, palladium and gold have been determined in 45 iron meteorites including representatives from all structural classes. Gallium was determined, in addition, in two specimens of troilite and in the metallic phase of two pallasites. The analytical procedures and the structural characteristics of the meteorites studied are described in detail. It is found that most

Edward Goldberg; Aiji Uchiyama; Harrison Brown

1952-01-01

314

Gallium arsenide differentially affects processing of phagolysosomal targeted antigen by macrophages.  

PubMed

Gallium arsenide, a semiconductor utilized in the electronics industry, causes immunosuppression in animals. The chemical's effect on macrophages to process antigen for activating pigeon cytochrome-specific helper T cell hybridoma was investigated. Mice were administered 200 mg/kg gallium arsenide or vehicle intraperitoneally. Five-day exposure suppressed processing by splenic macrophages but augmented processing by thioglycollate-elicited and resident peritoneal macrophages. Cytochrome coupled to latex beads was targeted to phagolysosomes to examine processing in lysosomes. Cytochrome beads required phagocytosis for processing and were located in phagolysosomes. Gallium arsenide did not alter the phagocytic ability of macrophages. Peritoneal macrophages normally processed the targeted antigen, indicating that gallium arsenide influenced compartment(s) preceding lysosomes. However, the processing efficiency of exposed splenic macrophages depended on the size of particulate cytochrome, suggesting that processing varied in phagolysosomes of different sizes. Gallium arsenide impacted different intracellular compartments in these macrophages, perhaps contributing to systemic immunotoxicity and local inflammation caused by exposure. PMID:9500519

Lewis, T A; Hartmann, C B; McCoy, K L

1998-03-01

315

Investigation of the variations in the crystallization front shape during growth of gadolinium gallium and terbium gallium crystals by the Czochralski method  

SciTech Connect

Numerical investigation of the variations in the crystallization front shape during growth of gadolinium gallium and terbium gallium garnet crystals in the same thermal zone and comparison of the obtained results with the experimental data have been performed. It is shown that the difference in the behavior of the crystallization front during growth of the crystals is related to their different transparency in the IR region. In gadolinium gallium garnet crystals, which are transparent to thermal radiation, a crystallization front, strongly convex toward the melt, is formed in the growth stage, which extremely rapidly melts under forced convection. Numerical analysis of this process has been performed within the quasistationary and nonstationary models. At the same time, in terbium gallium garnet crystals, which are characterized by strong absorption of thermal radiation, the phase boundary shape changes fairly smoothly and with a small amplitude. In this case, as the crystal is pulled, the crystallization front tends to become convex toward the crystal bulk.

Budenkova, O. N., E-mail: olganb@mail.ioffe.ru; Vasiliev, M. G.; Yuferev, V. S. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Ivanov, I. A.; Bul'kanov, A. M. [ZAO Research Institute of Materials Science (Russian Federation); Kalaev, V. V. [OOO Soft Impakt (Russian Federation)

2008-12-15

316

Measurement of achievable plutonium decontamination from gallium by means of PUREX solvent extraction  

SciTech Connect

The objective of the work described herein was to measure, experimentally, the achievable decontamination of plutonium from gallium by means of the PUREX solvent extraction process. Gallium is present in surplus weapons-grade plutonium (WG-Pu) at a concentration of approximately 1 wt%. Plans are to dispose of surplus WG-Pu by converting it to UO{sub 2}-PuO{sub 2} mixed oxide (MOX) fuel and irradiating it in commercial power reactors. However, the presence of high concentrations of gallium in plutonium is a potential corrosion problem during the process of MOX fuel irradiation. The batch experiments performed in this study were designed to measure the capability of the PUREX solvent extraction process to separate gallium from plutonium under idealized conditions. Radioactive tracing of the gallium with {sup 72}Ga enabled the accurate measurement of low concentrations of extractable gallium. The experiments approximated the proposed flowsheet for WG-Pu purification, except that only one stage was used for each process: extraction, scrubbing, and stripping. With realistic multistage countercurrent systems, much more efficient separations are generally obtained. The gallium decontamination factor (DF) obtained after one extraction stage was about 3 x 10{sup 6}. After one scrub stage, all gallium measurements were less than the detection limit, which corresponded to DFs >5 x 10{sup 6}. All these values exceed a 10{sup 6} DF needed to meet a hypothetical 10-ppb gallium impurity limit in MOX fuel. The results of this study showed no inherent or fundamental problem with regard to removing gallium from plutonium.

Collins, E.D.; Campbell, D.O.; Felker, L.K.

2000-01-01

317

Modified silicon-germanium alloys with improved performance. [thermoelectric material  

NASA Technical Reports Server (NTRS)

This paper discusses the results of a program on the modification of silicon-germanium alloys by means of small extraneous material additions in order to improve their figures-of-merit. A review of the properties that constitute the figure-of-merit indicates that it is the relatively high thermal conductivity of silicon-germanium alloys that is responsible for their low values of figure-of-merit. The intent of the effort discussed in this paper is therefore the reduction of the thermal conductivity of silicon-germanium alloys by minor alloy additions and/or changes in the basic structure of the material. Because Group III and V elements are compatible with silicon and germanium, the present effort in modifying silicon-germanium alloys has concentrated on additions of gallium phosphide. A significant reduction in thermal conductivity, approximately 40 to 50 percent, has been demonstrated while the electrical properties are only slightly affected as a result. The figure-of-merit of the resultant material is enhanced over that of silicon-germanium alloys and when fully optimized is potentially better than that of any other presently available thermoelectric material.

Pisharody, R. K.; Garvey, L. P.

1978-01-01

318

Melting points of gallium and of binary eutectics with gallium realized in small cells  

Microsoft Academic Search

Melting\\/freezing curves are studied for the single-component Ga and bimetallic eutectic alloys Ga-In, Ga-Sn, Ga-Zn and Ga-Al in small-size cells. These phase-transition studies were conducted at VNIIOFI and SDL in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous platforms. Our prime objective is to develop technology to improve the long-term performance of in-flight blackbody

A. Burdakin; B. Khlevnoy; M. Samoylov; V. Sapritsky; S. Ogarev; A. Panfilov; G. Bingham; V. Privalsky; J. Tansock; T. Humpherys

2008-01-01

319

Aluminum alloy  

NASA Technical Reports Server (NTRS)

This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

Blackburn, Linda B. (inventor); Starke, Edgar A., Jr. (inventor)

1989-01-01

320

Structure, electronic properties, and defects of amorphous gallium arsenide  

NASA Astrophysics Data System (ADS)

We have constructed a structural model of amorphous gallium arsenide by quenching from the melt, via first-principles molecular-dynamics simulations. The properties of our structure agree well with the available experimental information. We find that the predominant defects in this system are not wrong bonds, but threefold-coordinated atoms. Because of a relaxation mechanism similar to that occurring on the GaAs(110) surface, these do not yield states in the gap, but yield empty Ga and filled As dangling-bond states near the band edges.

Fois, E.; Selloni, A.; Pastore, G.; Zhang, Q.-M.; Car, R.

1992-06-01

321

Gallium uptake in tryptophan-related pulmonary disease  

SciTech Connect

We describe a patient who developed fever, fatigue, muscle weakness, dyspnea, skin rash, and eosinophilia after taking high doses of tryptophan for insomnia for two years. A gallium-67 scan revealed diffuse increased uptake in the lung and no abnormal uptake in the muscular distribution. Bronchoscopy and biopsy confirmed inflammatory reactions with infiltration by eosinophils, mast cells, and lymphocytes. CT scan showed an interstitial alveolar pattern without fibrosis. EMG demonstrated diffuse myopathy. Muscle biopsy from the right thigh showed an inflammatory myositis with eosinophilic and lymphocytic infiltrations.

Kim, S.M.; Park, C.H.; Intenzo, C.M.; Patel, R. (Thomas Jefferson Univ. Hospital, Philadelphia, PA (USA))

1991-02-01

322

Lasing action in gallium nitride quasicrystal nanorod arrays.  

PubMed

We report the observation of lasing action from an optically pumped gallium nitride quasicrystal nanorod arrays. The nanorods were fabricated from a GaN substrate by patterned etching, followed by epitaxial regrowth. The nanorods were arranged in a 12-fold symmetric quasicrystal pattern. The regrowth grew hexagonal crystalline facets and core-shell multiple quantum wells (MQWs) on nanorods. Under optical pumping, multiple lasing peaks resembling random lasing were observed. The lasing was identified to be from the emission of MQWs on the nanorod sidewalls. The resonant spectrum and mode field of the 12-fold symmetric photonic quasicrystal nanorod arrays is discussed. PMID:22714233

Chang, Shih-Pang; Sou, Kuok-Pan; Chen, Chieh-Han; Cheng, Yuh-Jen; Huang, Ji-Kai; Lin, Chung-Hsiang; Kuo, Hao-Chung; Chang, Chun-Yen; Hsieh, Wen-Feng

2012-05-21

323

3p photoionization and subsequent Auger decay of atomic gallium  

NASA Astrophysics Data System (ADS)

The 3p photoionization and subsequent Coster-Kronig type of Auger decay of initially neutral atomic gallium were studied both experimentally and theoretically. The binding energies and relative intensities of the 3p photoelectron spectrum together with a satellite structure are given. The M2, 3MM and M2, 3MN Auger electron spectrum leading to doubly ionized final states is presented. The synchrotron radiation excited photoelectron and Auger electron spectra were interpreted using multiconfiguration Dirac-Fock calculations providing spectral identification for the main observed features.

Anin, D.; Huttula, S.-M.; Huttula, M.

2013-09-01

324

Gallium-doped germanium, evaluation of photoconductors, part 1  

NASA Technical Reports Server (NTRS)

Gallium-doped germanium far infrared detectors were evaluated at low temperatures and low background simulating the space environment. Signal and noise characteristics were determined for detector temperatures in the 2K to 4K range. Optimum performance occurs at about 2.5K for all devices tested. The minimum average NEP in the 40-130 micron region was found to be approximately 4 x 10 to the minus 17th power watt Hz(-1/2) at a frequency of 1 Hz.

Moore, W. J.

1979-01-01

325

Technetium-99m DTPA aerosol and gallium scanning in acquired immune deficiency syndrome  

SciTech Connect

In 11 non-smoking AIDS patients suspected of pneumocystis carinii pneumonia (PCP), the results of Tc-99m DTPA aerosol clearances, gallium scans, and arterial blood gases were compared with those of bronchoalveolar lavage (BAL). Nine patients had PCP. All had increased clearances five times higher than the normal (5.6 +/- 2.3% X min-1 vs 1.1 +/- 0.34% X min-1, N = 10, P less than 0.001), suggesting an increased alveolar permeability. Gallium scans were abnormal in six patients but normal or slightly abnormal in the three others. Four of these nine patients had normal chest x-rays. In two of these the gallium scan was abnormal, but in the two others, only the increased Tc-99m DTPA clearances showed evidence of lung disease. Two patients had normal BAL, with normal clearances and gallium scans. Four out of the nine patients with PCP were studied after treatment. Three recovered and had normal clearance and gallium scans. One still had PCP with increased clearance but normal gallium scan. Gallium scanning and Tc-99m DTPA clearance are useful for detecting lung disease in AIDS patients with suspected PCP and for prompting BAL when chest x-rays and PaO/sub 2/ levels are normal. Due to its high sensitivity, a normal Tc-99m DTPA clearance could avoid BAL.

Picard, C.; Meignan, M.; Rosso, J.; Cinotti, L.; Mayaud, C.; Revuz, J.

1987-07-01

326

Synthesis, characterization, and X-ray crystal structure of a gallium monohydroxide and a hetero-bimetallic gallium zirconium oxide.  

PubMed

A monomeric hydroxide of gallium, LGa(Me)OH, containing terminal hydroxide and methyl groups was prepared by the hydrolysis of LGa(Me)Cl in the presence of N-heterocyclic carbene and water [L = HC{(CMe)(2,6-i-Pr2C6H3N)}2] in high yield and in a pure form. LGa(Me)OH was used as a synthon to assemble the first hetero-bimetallic compound with a Ga-O-Zr core, [(LGaMe)(Cp2ZrMe)](mu-O). PMID:16441096

Singh, Sanjay; Jancik, Vojtech; Roesky, Herbert W; Herbst-Irmer, Regine

2006-02-01

327

A hypothesis for anti-nanobacteria effects of gallium with observations from treating kidney disease.  

PubMed

Nanobacteria, 100-fold smaller than common bacteria, have been purported to exist in urine, and by precipitating calcium and other minerals into carbonate apatite around themselves, induce the formation of surrounding kidney stones. Nanobacteria-like structures have also been shown in blood, within arteries, aortic aneurysms, and cardiac valves. Gallium has antibiotic properties to iron-dependent bacteria and has potent anti-inflammatory, anticancer and anti-hypercalcemic properties, and it readily reverses osteoporosis. It was hypothesized that gallium nitrate might have benefit in treating kidney stones. Gallium nitrate (120mg gallium) was mixed with water making two liters of a gallium mineral water drink to treat chronic, treatment-resistant kidney stone pain and urinary tract bleeding in a 110 pound woman. On the third day of gallium mineral water treatment, the urine appeared snow white, thick (rope-like) and suggestive of a calcific crystalline nature. After release of the white urine, the urine returned to normal in color, viscosity and pH, kidney pain was no longer present, and there was no further evidence of blood in the urine. There were no treatment side effects or sequela. For a one year observation period thereafter, no kidney stones, white urine, kidney or urinary tract pain or blood in the urine was noted. The hypothetical susceptibility of nanobacteria to gallium treatment also suggests application to atherosclerosis and other diseases. Although some support for gallium in treating kidney stones is presented, this hypothesis is built upon another hypothesis, is extremely speculative, and alternative explanations for the white urine exist. Further research into gallium's effects on kidney disease and other nanobacteria-induced diseases such as cardiovascular diseases is suggested. PMID:18579317

Eby, George A

2008-10-01

328

High-surface Thermally Stable Mesoporous Gallium Phosphates Constituted by Nanoparticles as Primary Building Blocks  

SciTech Connect

In constant, search for micro/mesoporous materials, gallium phosphates, have attracted continued interest due to the large pore size reported for some of these solids in comparison with analogous aluminum phosphates. However up to now, the porosity of gallium phosphates collapsed upon template removal or exposure to the ambient moisture. In the present work, we describe high-surface thermally stable mesoporous gallium phosphates synthesized from gallium propoxide and PCl{sub 3} and different templating agents such as amines (dipropylamine, piperidine and aminopiperidine) and quaternary ammonium salts (C{sub 16}H{sub 33}(CH{sub 3})3NBr and C{sub 16}PyCl). These highly reactive precursors have so far not been used as gallium and phosphate sources for the synthesis of gallophosphates. Conceptually, our present synthetic procedure is based on the fast formation of gallium phosphate nanoparticles via the reaction of gallium propoxide with PCl{sub 3} and subsequent construction of the porous material with nanoparticles as building blocks. The organization of the gallophosphate nanoparticles in stable porous structures is effected by the templates. Different experimental procedures varying the molar composition of the sol-gel, pH and the pretreatment of gallium precursor were assayed, most of them leading to satisfactory materials in terms of thermal stability and porosity. In this way, a series of gallium phosphates with surface are above 200 m{sup 2} g{sup -1}, and narrow pore size from 3 to 6 nm and remarkable thermal stability (up to 550 C) have been prepared. In some cases, the structure tends to show some periodicity and regularity as determined by XRD. The remarkable stability has allowed us to test the catalytic activity of gallophosphates for the aerobic oxidation of alkylaromatics with notable good results. Our report reopens the interest for gallophosphates in heterogeneous catalysis.

V Parvulescu; V Parvulescu; D Ciuparu; C Hardacre; H Garcia

2011-12-31

329

[Determination of traces of gallium in air by oscillographic polarography].  

PubMed

Gallium and its compounds in air collected by millipore filter membrane are leached by 10% HNO3 at room temperature. After being adjusted with ammonia solution to pH8-9, the leachate is filtered and the filtrate is evaporated to dryness on a water bath. The residue is dissolved with 2 ml of 10% HNO3 and then into the solution are added 0.5 ml of 5% hydroxylamine hydrochloride solution, 0.20 ml of 5% sulfosalicyclic acid solution, 0.5 ml of NaF solution (1mg F/ml) and 1 drop of methyl red solution. Let it stand for 5 min after the color of the solution turns orange by addition of 1:1 NH4OH solution. Add 0.20ml of 0.20% cupferron solution, 0.20ml of 0.5% diphenyl-guanidine solution (prepared in 95% ethanol) and 0.5ml of acetic acid-ammonium acetate buffer (pH 7.0). Then add water to make the final volume of the test solution to be 10ml and measure the height of the second derivative polarographic wave at -1.08V (vs.SCE). The sensitivity of the method is 0.005-0.10 microgram/ml, the coefficient of variation 6.8%, recovery 97.8%. Within 0.005-0.10 microgram/ml, the wave height is linear with the concentration of gallium. PMID:2365333

Sun, C; Yang, Z; Cheng, D; Yi, Z; Shen, T; Liu, Z; Bai, Y

1990-03-01

330

Experimental investigation of electron transport properties of gallium nitride nanowires  

NASA Astrophysics Data System (ADS)

We report transport properties of gallium nitride (GaN) nanowires grown using direct reaction of ammonia and gallium vapor. Reliable devices, such as four-terminal resistivity measuring structures and field-effect transistors, were realized by dielectrophoretically aligning the nanowires on an oxidized silicon substrate and subsequently applying standard microfabrication techniques. Room-temperature resistivity in the range of (1.0-6.2)×10-2 ? cm was obtained for the nanowires with diameters ranging from 200 to 90 nm. Temperature-dependent resistivity and mobility measurements indicated the possible sources for the n-type conductivity and high background charge carrier concentration in these nanowires. Specific contact resistance in the range of 5.0×10-5 ? cm2 was extracted for Ti/Al/Ti/Au metal contacts to GaN nanowires. Significant reduction in the activation energy of the dopants at low temperatures (<200 K) was observed in the temperature-dependent resistivity measurement of these nanowires, which is linked to the onset of degeneracy. Temperature-dependent field-effect mobility measurements indicated that the ionized impurity scattering is the dominant mechanism in these nanowires at all temperatures.

Motayed, Abhishek; Davydov, Albert V.; Mohammad, S. N.; Melngailis, John

2008-07-01

331

Gallium nitride microcavities formed by photoenhanced wet oxidation  

NASA Astrophysics Data System (ADS)

We report the formation of gallium nitride (GaN) microcavities by manipulating a photoenhanced oxidation rate difference between the polar and nonpolar crystallographic planes of GaN. When immersed in a buffered acetic (CH3COOH) electrolyte of pH~6.2 at room temperature, it is shown that the photo-oxidation can proceed at a rate that is one order of magnitude slower on the nonpolar plane of {1100}GaN than on the polar plane of {0001}GaN due to the reduced surface field action. Gallium nitride microcavities bounded by optically smooth {1100} and {1103} facets can thus be preferentially formed on the c-plane sapphire substrate after dissolving the oxide layer. The optical properties of these GaN hexagonal cavities reveal characteristic peaks of whispering gallery modes in resonance with the GaN band edge emission spectrum. A typical cavity Q factor of 103 is observed in these GaN microcavities due to a reduced optical scattering loss in the wet chemical reaction process.

Peng, L.-H.; Lu, C.-Y.; Wu, W.-H.; Wang, S.-L.

2005-10-01

332

Adsorptive stripping voltammetric determination of chromium in gallium.  

PubMed

The electroanalytical chemistry of trace metals has progressed strongly with the development of cathodic stripping voltammetry (CSV) preceded by adsorption collection of organic metal complexes. A sensitive method for the determination of trace amount of chromium in gallium is described. Gallium is dissolved in sodium hydroxide containing hydrogen peroxide. The method is based on the catalytic activity of nitrate ions on the reduction of Cr(III)TTHA (triethylene tetramine-N,N,N',N'',N''',N'''-hexaacetic acid) complex. The sensitivity of this method is further improved by adsorption preconcentration of Cr(III)TTHA complex at a hanging mercury drop electrode (HMDE). The Cr(III) formed at the electrode surface by the reduction of Cr(VI), which is present in the bulk solution, is immediately complexed by TTHA. The adsorbed complex is then reduced at a peak potential of - 1.26 V, and the peak height of Cr(III) reduction is measured. The determination limit was restricted by the amount of chromium present in the reagent blank solution. The method is suitable for the determination of chromium at level as low as 0.2 mug g(-1) (with about 50 mg of sample) and a relative standard deviation of 15%. PMID:18967023

Palrecha, M M; Mathur, P K

1997-12-19

333

Biochemical mechanism of gallium on prevention of fatal cage-layer osteoporosis.  

PubMed

The possible biochemical mechanism of gallium was studied in this paper. One-day-old hens were fed to up to 68 weeks on a control diet and diets containing gallium. Serum calcium and phosphorus, serum alkaline phosphatase, tartrate resistant acid phosphatase (TRAP), serum osteocalcin, homocysteine, C-terminal crosslinked telopeptides of collagen type I, and bone mineral content were measured, respectively. The beneficial effects of gallium supplementation on improvement of cage layer osteoporosis were attributable mainly to decrease TRAP activity, C-terminal crosslinked telopeptides of collagen type I level, plasma calcium and phosphate concentrations, and increase the mineral content in the bones and osteocalcin level in plasma. PMID:19639269

Li, Chunxiang; Jiang, Zheng; Liu, Xinghan

2010-05-01

334

First-principles study of the connection between structure and electronic properties of gallium  

NASA Astrophysics Data System (ADS)

Different structures of gallium have been studied by means of density-functional theory. The density of states of orthorhombic ?-Ga , the only elemental solid exhibiting both metallic and molecular characters at zero pressure, shows a pseudogap at the Fermi energy. Complex analysis of the relation between lattice structure and the corresponding electronic properties allows us to throw light upon an origin of the pseudogap. We have found that the free-electron-like behavior which is a property of the high-pressure bct and fcc phases of gallium depends strongly on the arrangement of atoms in the buckled planes, one of the building blocks of the orthorhombic gallium.

Voloshina, Elena; Rosciszewski, Krzysztof; Paulus, Beate

2009-01-01

335

Unilateral gallium-67 uptake in primary tuberculosis of the major salivary glands  

SciTech Connect

Unilateral radionuclide accumulation in salivary glands is an uncommon finding on gallium scintigraphy. The differential diagnosis includes malignant tumors and inflammatory processes of these organs. Two cases of unilateral gallium uptake of the parotid and submandibular gland respectively, verified as solitary tuberculosis, are presented, together with the correlative findings of Tc-99m pertechnetate scintigraphy, sialography, and sonography. None of these imaging modalities is specific enough to provide pathognomonic signs for tuberculosis. When assessing unilateral gallium uptake of the salivary glands, one should be aware of the possibility of tuberculosis.

Bihl, H.; Maier, H.

1987-08-01

336

Photochemistry of trimethylgallium with application to atomic gallium reaction kinetics. [Trimethylgallium  

SciTech Connect

The photodissociation of gas-phase trimethylgallium at 193 nm has been investigated using the laser photolysis/laser induced fluorescence technique. Gallium atoms are produced by multiple-photon processes during the time of the excimer laser pulse and continue to be produced at long times after the photolysis pulse. The observed dependences on photolysis laser fluence, trimethylgallium pressure, and buffer gas pressure are consistent with a mechanism in which highly excited gallium methyl radicals undergo unimolecular decomposition to produce gallium atoms. Since this process can happen on time scales long compared to the photolysis laser pulse, these results may have important implications for studies of laser deposition of thin metal films.

Baughcum, S.L.; Oldenborg, R.C.

1985-01-01

337

LETTER TO THE EDITOR: Fabrication and structure of an opal-gallium nitride nanocomposite  

NASA Astrophysics Data System (ADS)

A three-dimensional gallium nitride lattice has been synthesized within the void sublattice of an artificial opal. The composite structure has been characterized using X-ray diffraction, Raman spectroscopy and transmission electron microscopy.

Davydov, V. Yu; Dunin-Borkovski, R. E.; Golubev, V. G.; Hutchison, J. L.; Kartenko, N. F.; Kurdyukov, D. A.; Pevtsov, A. B.; Sharenkova, N. V.; Sloan, J.; Sorokin, L. M.

2001-02-01

338

Ultra-Low Power Fiber-Coupled Gallium Arsenide Photonic Crystal Cavity Electro-Optical Modulator.  

National Technical Information Service (NTIS)

We demonstrate a gallium arsenide photonic crystal cavity injection- based electro-optic modulator coupled to a fiber taper waveguide. The fiber taper serves as a convenient and tunable waveguide for cavity coupling with minimal loss. Localized electrical...

A. Majumdar B. Ellis E. E. Haller G. Shambat M. A. Mayer

2011-01-01

339

Utility of gallium imaging of the kidneys in diagnosing primary amyloid nephrotic syndrome  

SciTech Connect

We undertook a study to determine the value of gallium imaging of the kidneys in patients who had primary amyloidosis that was manifest clinically by nephrotic syndrome. We studied 28 patients with gallium-67 (67Ga) citrate scans performed 48 hr after injection. Intense (3+ to 4+) uptake was noted in both kidneys in 25 of 28 patients. Renal amyloidosis should be considered in the differential diagnosis when diffuse bilateral renal uptake of (67Ga)citrate is seen in the setting of nephrotic syndrome. Gallium uptake did not differentiate amyloid nephrotic syndrome from other causes of nephrotic syndrome. Renal gallium uptake showed a weak correlation with 24-hr urine protein excretion (p = 0.06).

Gertz, M.A.; Brown, M.L.; Hauser, M.F.; Kyle, R.A. (Mayo Clinic, Rochester, MN (USA))

1990-03-01

340

Polycrystalline Thin-Film Research: Copper Indium Gallium Diselenide (Fact Sheet)  

SciTech Connect

Capabilities fact sheet for the National Center for Photovoltaics: Polycrystalline Thin-Film Research: Copper Indium Gallium Diselenide that includes scope, core competencies and capabilities, and contact/web information.

Not Available

2011-06-01

341

Analysis of gallium arsenide deposition in a horizontal chemical vapor deposition reactor using massively parallel computations.  

National Technical Information Service (NTIS)

A numerical analysis of the deposition of gallium from trimethylgallium (TMG) and arsine in a horizontal CVD reactor with tilted susceptor and a three inch diameter rotating substrate is performed. The three-dimensional model includes complete coupling be...

A. G. Salinger J. N. Shadid S. A. Hutchinson

1998-01-01

342

An Intercomparison of Sealed Cells for Realizing the Melting and Triple Points of Gallium  

Microsoft Academic Search

Cells for the realization of the melting and triple points of gallium were prepared at NPL, INM and IMGC. One cell of each manufacture has been measured at NPL, IMGC, INM, PTB, JTI and SM, using both a \\

M. V. Chattle; R. L. Rusby; G. Bonnier; A. Moser; E. Renaot; P. Marcarino; G. Bongiovanni; G. Frassineti; W. Neubert; H. G. Fuhrmann; I. Wessel; H. Voorhof

1987-01-01

343

Gallium Content in PuO{sub 2} Using Laser Induced Breakdown Spectroscopy (LIBS)  

SciTech Connect

Laser Induced Breakdown Spectroscopy (LIBS) has been applied to the semi-quantitative analysis of gallium in plutonium oxide at the Los Alamos Plutonium Facility. The oxide samples were generated by the Thermally Induced Gallium Removal (TIGR) process, a pretreatment step prior to MOX fuel processing. The TIGR process uses PuO{sub 2} containing 1 wt% gallium (nominal) as feed material. Following the TIGR process, gallium content was analyzed by LIBS and also by conventional wet chemical analysis (ICP-MS). Although the data range was insufficient to obtain an adequate calibration, general agreement between the two techniques was good. LIBS was found to have a useful analytical range of 34-400 ppm for Ga in PuO{sub 2}.

Smith, C.A.; Martinez, M.A.; Veirs, D.K.

1999-08-29

344

Preliminary Survey Report: Control Technology for Gallium Arsenide Processing at Honeywell, Inc., Richardson, Texas,  

National Technical Information Service (NTIS)

An evaluation was made of control technology at Honeywell, Inc., (SIC-3674) in Richardson, Texas, which was primarily involved in gallium-arsenide (1303000) wafer fabrication involving about 70 workers. Major hazards were potential chemical exposures to s...

K. L. Lenihan

1987-01-01

345

Assembly and Packaging of Microwave Gallium Arsenide Devices for the Space Environment.  

National Technical Information Service (NTIS)

Work carried out investigating the placement, wire bonding and packaging of gallium arsenide devices for space applications is described. Selection of adhesives for die placement and lid sealing and comparison with a gold/tin eutectic for the same process...

C. Wescott

1991-01-01

346

Solvent extraction and separation of gallium, indium and thallium with N-benzylaniline.  

PubMed

A simple and rapid method is proposed for the separation of tervalent gallium, indium and thallium by solvent extraction with N-benzylaniline in chloroform from different concentrations of hydrochloric acid. Thallium and gallium are extracted from 1M and 7.0-7.5M hydrochloric acid respectively. Indium is finally extracted from hydriodic acid. These metals in the final extracts are determined complexometrically. Interference from some cations can easily be eliminated by reduction with sulphite, followed by selective oxidation of thallium(I) to thallium(III) with saturated bromine water, and from others by the use of thioglycollic acid as a masking agent in the extraction of gallium and indium. Most common anions cause no interference. Log-log plots of distribution coefficients vs. concentration of amine for gallium, indium and thallium indicate a 2:1 limiting mole ratio of amine to these metals. PMID:18961477

Khosla, M M; Singh, S R; Rao, S P

1974-06-01

347

Gallium-67 scintigraphy, bronchoalveolar lavage, and pathologic changes in patients with pulmonary sarcoidosis  

SciTech Connect

The intensity of gallium-67 scintiscans, lymphocyte counts in bronchoalveolar lavage fluid, and pathologic changes were studied in 26 patients with untreated pulmonary sarcoidosis. Noncaseating granulomas were recognized with significantly greater frequency in stage 2 (80 percent; 8/10 cases) than in stage 1 (43 percent; 6/14 cases). Alveolitis showed little relation to the roentgenographic stage. There was a strong correlation between the intensity of gallium uptake in pulmonary parenchyma and the detection rate of granuloma; however, the detection rate of alveolitis was not statistically different from the intensity of gallium uptake. A highly significant correlation was revealed between the lymphocyte counts in bronchoalveolar lavage fluid and the intensity of alveolitis. These observations suggest that the gallium uptake reflects mainly the presence of granuloma, and the lymphocyte count in bronchoalveolar lavage fluid reflects the intensity of alveolitis in patients with pulmonary sarcoidosis.

Abe, S.; Munakata, M.; Nishimura, M.; Tsuneta, Y.; Terai, T.; Nakano, I.; Ohsaki, Y.; Kawakami, Y.

1984-05-01

348

Efficient bifunctional gallium-68 chelators for positron emission tomography: tris(hydroxypyridinone) ligands  

PubMed Central

A new tripodal tris(hydroxypyridinone) bifunctional chelator for gallium allows easy production of 68Ga-labelled proteins rapidly under mild conditions in high yields at exceptionally high specific activity and low concentration.

Berry, David J.; Ma, Yongmin; Ballinger, James R.; Tavare, Richard; Koers, Alexander; Sunassee, Kavitha; Zhou, Tao; Nawaz, Saima; Mullen, Gregory E. D.; Hider, Robert C.; Blower, Philip J.

2014-01-01

349

Separation of gallium and arsenic from the wafer grinding extraction solution.  

PubMed

This work investigates the separation of gallium and arsenic from the wafer grinding extraction solution. The wafer grinding extraction solution was generated using hot and concentrated nitric acid. In this study, adsorption technology was employed to remove the toxic arsenic from the extraction solution. Ferric hydroxide was the adsorbent employed to adsorb arsenic. The effects of pH value, contact time, absorbent dosage, and chloride ion concentration on the efficiency of adsorption of gallium and arsenic were investigated. The optimal conditions for recovering gallium and removing arsenic were a raw pH of 0.2, a contact time of 6min and a ferric hydroxide concentration of 30.4g/L. Additionally, adding chloric ions reduces the residual percentage of gallium (ReGa) and the percentage of arsenic removed (RAs). Under these optimal conditions, ReGa and RAs are 100 and 80%, respectively. PMID:15478937

Chen, Yi-Fu; Yang, Fong-Ru; Jean, Jeng-Shyong; Tsai, Chin-Ying

2004-01-01

350

Determination of gallium concentration in blood-free tissues using a radiolabeled blood marker  

SciTech Connect

Radioiodinated serum albumin has been used as a blood marker to define and quantitate physiological volumes for 12 organs and tissue types. The concentration of gallium-67 in blood-free tissues of rats was also determined at various times after intravenous administration. Tissues were divided into two kinetically distinguishable types based on reported nonuniform distribution of the blood marker and the gallium distribution observed in the present study. Gallium distribution into the liver and spleen was observed to be slow, with a discernable accumulation phase followed by monoexponential elimination. In contrast, gallium accumulation into the stomach, small and large intestines, heart, lung, skin/adipose tissue, and muscle was rapid and elimination was monophasic.

Triplett, J.W.; Hayden, T.L.; McWhorter, L.K.; Gautam, S.R.; Kim, E.E.; Bourne, D.W.

1985-09-01

351

Process for producing gallium-containing solution from the aluminum smelting dust  

SciTech Connect

A process is described for producing a gallium-containing solution from aluminum smelting dust comprising leaching aluminum smelting dust with a mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid, and adding an oxidizing agent to the aluminum smelting dust at the time of leaching to preferentially leach and extract gallium from the aluminum smelting dust without extracting aluminum from the aluminum smelting dust. The oxidizing agent is selected from the group consisting of potassium permanganate, manganese dioxide, hydrogen peroxide, ozone, potassium chromate, potassium dichromate, ammonium persulfate, sodium hydrochlorite, sodium chlorite and sodium chlorate. The leached aluminum smelting dust is filtered to obtain a gallium-containing solution of dissolved gallium.

Era, A.; Matsui, S.; Ikeda, H.

1988-03-01

352

Growth and characterization of gallium indium nitrogen arsenide and gallium indium nitrogen phosphide  

NASA Astrophysics Data System (ADS)

Nitrogen incorporation into GaInAs and GaInP based on GaAs (100) substrates has attracted a great deal of attention due to their potential applications in ultra-high-efficiency multijunction solar cells as well as in optoelectronic devices. In order to investigate not yet well-studied material families of III-N-V compounds, we use gas-source molecule beam epitaxy (MBE) method, in which nitrogen radicals are used as the nitrogen precursor, to grow mixed group-V nitride alloy semiconductors with excellent crystallinity. This dissertation is divided into two major parts. In the first part, we use different structures to improve GaInNAs material quality, including strain-compensated GaIn0.08As/GaN0.03As and strained InAs/GaN0.03As0.97 short-period superlattices (SPSLs). The photoluminescence intensity of the SPSLs is 12 times higher than that of random alloys, while electron mobility is improved by a factor of two. InAs/GaN0.03As0.97 SPSL is very promising for 1.3 mum GaInNAs quantum well laser application. Photoconductance measurements show a type-II band lineup for the Ga0.92In0.08As/GaN 0.03As0.97 heterojunction. In the second part, we demonstrate the successful growth of a novel material, GaInNP. Fundamental optical and electrical transport properties of GaInNP are studied. Nitrogen incorporation dramatically reduces the GalnP band gap, which can be successfully explained by the band anticrossing model based on the concept of an anticrossing interaction between localized N states and the extended conduction band states. Rapid thermal annealing improves the optical properties, but decreases the free electron concentration because Si dopant is passivated by N through the formation of Si-N pairs. Band alignment between GaInNP and GaAs is also investigated. GaInNP is an ideal material for tunnel-collector heterojunction bipolar transistors (HBTs). In comparing the properties of GaInNP and GaInNAs, great similarities are found in terms of the effect of nitrogen incorporation. Here, the band anticrossing model successfully explains the band gap reduction and predicts an increase of the electron effective mass for both material.

Hong, Yuguang

353

VAl Alloy  

NASA Astrophysics Data System (ADS)

Power generation performance of a thermoelectric module consisting of the Heusler Fe2VAl alloy was evaluated. For construction of the module, W-doped Fe2VAl alloys were prepared using powder metallurgy process. Power generation tests of the module consisting of 18 pairs of p- n junctions were conducted on a heat source of 373-673 K in vacuum. The reduction of thermal conductivity and improvement of thermoelectric figure of merit by W-doping enhanced the conversion efficiency and the output power. High output power density of 0.7 W/cm2 was obtained by virtue of the high thermoelectric power factor of the Heusler alloy. The module exhibited good durability, and the relatively high output power was maintained after temperature cycling test in air.

Mikami, M.; Mizoshiri, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.

2014-06-01

354

Identification of a physical metallurgy surrogate for the plutonium-1 wt. % gallium alloy  

NASA Astrophysics Data System (ADS)

Future plutonium research is expected to be limited due to the downsizing of the nuclear weapons complex and an industry focus on environmental remediation and decommissioning of former manufacturing and research facilities. However, the need to further the understanding of the behavior of plutonium has not diminished. Disposition of high level residues, long-term storage of wastes, and certification of the nuclear stockpile through the Stockpile Stewardship Program are examples of the complex issues that must be addressed. Limited experimental facilities and the increasing cost of conducting plutonium research provide a strong argument for the development of surrogate materials. The purpose of this work was to identify a plutonium surrogate based on fundamental principles such as electronic structure, and then to experimentally demonstrate its viability. .

Gibbs, Frank E.; Olson, David L.; Hutchinson, William

2000-07-01

355

Controlled delivery of antimicrobial gallium ions from phosphate-based glasses.  

PubMed

Gallium-doped phosphate-based glasses (PBGs) have been recently shown to have antibacterial activity. However, the delivery of gallium ions from these glasses can be improved by altering the calcium ion concentration to control the degradation rate of the glasses. In the present study, the effect of increasing calcium content in novel gallium (Ga2O3)-doped PBGs on the susceptibility of Pseudomonas aeruginosa is examined. The lack of new antibiotics in development makes gallium-doped PBG potentially a highly promising new therapeutic agent. The results show that an increase in calcium content (14, 15 and 16 mol.% CaO) cause a decrease in degradation rate (17.6, 13.5 and 7.3 microg mm(-2) h(-1)), gallium ion release and antimicrobial activity against planktonic P. aeruginosa. The most potent glass composition (containing 14 mol.% CaO) was then evaluated for its ability to prevent the growth of biofilms of P. aeruginosa. Gallium release was found to reduce biofilm growth of P. aeruginosa with a maximum effect (0.86 log(10) CFU reduction compared to Ga2O3-free glasses) after 48 h. Analysis of the biofilms by confocal microscopy confirmed the anti-biofilm effect of these glasses as it showed both viable and non-viable bacteria on the glass surface. Results of the solubility and ion release studies show that this glass system is suitable for controlled delivery of Ga3+. 71Ga NMR and Ga K-edge XANES measurements indicate that the gallium is octahedrally coordinated by oxygen atoms in all samples. The results presented here suggest that PBGs may be useful in controlled drug delivery applications, to deliver gallium ions in order to prevent infections due to P. aeruginosa biofilms. PMID:18974026

Valappil, S P; Ready, D; Abou Neel, E A; Pickup, D M; O'Dell, L A; Chrzanowski, W; Pratten, J; Newport, R J; Smith, M E; Wilson, M; Knowles, J C

2009-05-01

356

Synthesis and single crystal growth of gallium phosphide by the liquid encapsulated vertical Bridgman technique  

Microsoft Academic Search

Gallium phosphide is a typical III–V compound semiconductor and is also an important electronic material. The synthesis and\\u000a single crystal growth of this compound by melt methods is rendered very difficult because of the large phosphorus vapour pressure.\\u000a A high pressure vessel with internal heating and a quartz reactor was first developed for the direct synthesis of gallium\\u000a phosphide. The

K Govinda Rajan; N V Chandra Shekar; G V N Rao; A J Singh; R M Iyer

1988-01-01

357

Gallium-67 scintigraphy in the evaluation of patients with clinical or laboratory evidence of hepatoma  

SciTech Connect

Previous reports had shown that gallium-67 accumulates in hepatoma in 70 to 100% of cases according to different authors. The authors evaluated the significance of Ga-67 scintigraphy in 50 patients, 45 cirrhotics and 5 with other problems. All the patients had either focal defects (44) or patchy uptake (6) on a Tc-99m sulphur colloid scintigram (SC). Routine Ga-67 scintigraphy (5mCi, 48-72 hours imaging, planar gamma camera, medium energy collimator, 2-3 peak energy use) was performed and evaluated in conjunction with the associated Tc-99m SC scintigraphy. Of the 50 pts. 25 had hepatomas. All of them had focal defects on Tc-99m SC scans and incongruent gallium images with either filling of the defects or hot spots. Alfafetoprotein was measured in 18 patients and was normal in 5. Of the remaining 25 pts. without hepatoma 22 had cirrhosis (16 had focal defects and 6 patchy uptake on Tc-99m SC images, but all showed congruent gallium distribution, alfafetoprotein was measured in 12 pts. and was abnormally high in 5) and 3 had abscess, lymphoma or adrenal carcinoma (all had focal defect on Tc-99m SC images and incongruent gallium distribution with hot spots filling the defects of the Tc SC scan). In the series gallium was found to be very useful in separating focal liver abnormalities on Tc-99 SCS in cirrhotics. When a lesion didn't take up gallium, no hepatoma was present. When a defects on SC scintigraphy disappeared or picked up more activity on gallium, the patient had hepatoma (25), or abscess (1), lymphoma (1), adrenal ca. (1). In no case cirrhotic scarring showed gallium uptake. Alfafetoprotein, however, was positive in 5 cirrhotics and negative in 5 hepatomas.

Gentili, A.; Sfakianakis, G.; Jeffers, L.J.; Reddy, K.; Schiff, E.; Serafini, A.N.

1985-05-01

358

First Results of the Testing of the Liquid Gallium Jet Limiter Concept for ISTTOK  

NASA Astrophysics Data System (ADS)

The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages to the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaustion from fusion devices. Presently the most promising materials are Lithium and Gallium. ISTTOK, a small size tokamak, will be used to test the behavior of a liquid Gallium jet in the vacuum chamber and its influence on the plasma. This paper presents a description of the conceived setup as well as experimental results. The liquid Gallium jet is generated by hydrostatic pressure and injected in a radial position close to a moveable stainless steel limiter. Both the jet and the limiter positions are variable allowing for a controlled exposure of the liquid Gallium to the edge plasma. The main components of the Gallium loop are a MHD pump, the liquid metal injector and a filtering system. The MHD pump is of the induction type, based on rotating permanent magnets. The injector is build from a ¼'' stainless steel pipe ended by a shaping nozzle. A setup has been developed to introduce oxide-free Gallium inside the loop's main supply tank. Raw liquid metal is placed inside a chamber heated and degassed under high vacuum while clean Gallium is extracted from the main body of the liquefied metal. Prior to installation on the tokamak, the experimental rig has been implemented using a Pyrex tube as test chamber to investigate the stability of the Gallium jet and its break-up length for several nozzle sizes. Results are presented in this paper. This rig was also useful to assess the behavior of the overall implemented apparatus.

Gomes, R. B.; Fernandes, H.; Silva, C.; Borba, D.; Carvalho, B.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Mikelsons, A.; Platnieks, I.

2006-12-01

359

Solvent Extraction of Gallium (III) from Basic Sodium Aluminate Solution by Alkanoyl Oxines  

Microsoft Academic Search

Alkanoyl oxines have been used for the extraction of gallium from basic solution, especially for the selective recovery of gallium in the presence of excess aluminum from Bayer process sodium aluminate liquor. 5-Alkanoyl-8-hydroxyquinolines (R.CO.Ox), where R is the alkyl group C13H27 (myristoyl), C15H31 (palmitoyl), and C17H35 (stearoyl) were synthesized by the Fries rearrangement from the corresponding acid chloride and sodium

H. Filik; R. Apak

1994-01-01

360

Defect reactions in gallium antimonide studied by zinc and self-diffusion  

Microsoft Academic Search

Extrinsic diffusion of zinc (Zn) in gallium antimonide (GaSb) under Ga-rich conditions was analyzed on the basis of the kick-out and the dissociative diffusion mechanism. It is concluded that the changeover of interstitial Zn to substitutional gallium (Ga) sites is mainly mediated by Ga interstitials (IGa). Fitting of the Zn profiles provides the relative contributions of IGa to Ga diffusion.

Kirsten Sunder; Hartmut Bracht

2007-01-01

361

Early supradiaphragmatic Hodgkin's disease. High-dose gallium scanning obviates the need for staging laparotomy  

SciTech Connect

Experience with 16 sequential patients with Stage IA/IIA supradiaphragmatic Hodgkin's disease who had no evidence of intra-abdominal disease using high-dose gallium and computerized tomography scanning is reported. Subsequent staging laparotomy also was negative in all these patients and did not alter management decisions. It is suggested that high-dose, whole-body gallium scanning and other noninvasive staging procedures give reliable data for therapeutic decisions.

Blackwell, E.A.; Joshua, D.E.; McLaughlin, A.F.; Green, D.; Kronenberg, H.; May, J.

1986-08-15

362

Tumoral calcinosis associated with sarcoidosis and positive bone and gallium imaging  

SciTech Connect

A 63-year-old female with biopsy proven tumoral calcinosis presented with progressive and recurrent swelling and tenderness of the right hip, thigh, elbow, and wrist. Both gallium and bone imaging demonstrated intense, congruent uptake in these areas. This is the third case of tumoral calcinosis with sarcoidosis documented in the literature. However, these are the first published bone and gallium scans in a patient with a history of sarcoidosis and tumoral calcinosis.

Wolpe, F.M.; Khedkar, N.Y.; Gordon, D.; Werner, P.; Shirazi, P.; Al-Sabban, M.H.

1987-07-01

363

Are oral cathartics of value in optimizing the gallium scan? Concise communication.  

PubMed

The normal intestinal secretion of 9-15% of an administered dose of gallium-67 may prevent early detection of intra-abdominal disease. We randomized 50 patients to receive either no bowel preparation or 30 cc of milk of magnesia plus 5 cc of cascara. No significant difference was found between the two groups in frequency with which gallium interfered with readings or time to complete the study. PMID:7218018

Silberstein, E B; Fernandez-Ulloa, M; Hall, J

1981-05-01

364

The Soviet-American gallium-germanium experiment on the detection of solar neutrinos  

Microsoft Academic Search

The Soviet-American gallium-germanium (GG) experiment on solar-neutrino detection will be carried out at the Baksan neutrino observatory. The GG neutrino telescope is situtated 3500 meters below ground. The system with 30 tons of gallium is ready for operation and it is expected that the first results will be obtained in 1989; after a year of measurements the results are expected

A. I. Abazov; D. N. Abdurashitov; A. V. Avdeev; O. L. Anosov; Iu. A. Belous'ko

1989-01-01

365

[Experimental studies on the systemic toxicity of dental alloys free of precious metals].  

PubMed

The systemic toxicity of five non-precious dental alloys was evaluated by help of an animal study. The pulverized dental alloys, filled in gelatine capsules, were orally administered to laboratory rats using a special esophageal application device. For each alloy examined randomized groups of ten experimental animals and ten control animals were used. For a period of seven days the experimental animals received daily 1000 mg alloy powder per kilogram body-weight. The animals of the control groups received daily empty gelatine capsules (placebo application). After two weeks all animals were killed and autopsies of the animals were performed. Histopathologic examinations of the lungs, kidneys, liver, small intestine and large intestine of all animals were done. With statistic significance (p less than 0.001) rats whom nickel-chromium alloys were administered orally showed serious pathologic reactions more frequently than placebo-treated control animals. Nickel-chromium alloys containing beryllium and/or gallium caused the strongest organic lesions. In contrary to this a dental cobalt-chromium alloy showed a very low systemic toxicity. The results of the study underline that preclinical toxicity testing of dental alloys is necessary in order to avoid systemic toxic lesions in man. PMID:1496349

Reuling, N; Fuhrmann, R; Keil, M

1992-01-01

366

A study of surface tension driven segregation in monotectic alloy systems  

NASA Technical Reports Server (NTRS)

The compatibilities of various monotectic alloy systems with several different crucible materials were evaluated. The study was carried out using small candidate alloy samples of compositions that produced fifty volume percent of each liquid phase at the monotectic temperature. Compatibility was based on the evaluation of the wetting tendency of the two immiscible phases with the crucible material in a one-g solidified sample. Three types of wetting phenomena were observed during the evaluation. Type 1 indicates an alloy-crucible combination where the L2 phase preferentially wets the crucible material. Since L2 is usually the minority phase in desirable alloys, this material combination would be difficult to process and is therefore considered incompatible. Type 2 behavior indicates an alloy-crucible combination where the L1 phase preferentially wets the crucible material. This type of combination is considered compatible since surface tension effects should aid in processing the alloy to a useful form. Type 3 indicates any combination that leads to major reactions between the alloy and crucible material, gas entrapment, or separation of the metal from the crucible wall. Additional compatibility evaluations would have to be carried out on combinations of this category. The five alloy systems studied included aluminum-bismuth, copper-lead, aluminum-indium, aluminum-lead and cadmium-gallium. The systems were combined with crucibles of alumina, boron nitride, mullite, quartz, silicon carbide and zirconia.

Andrews, J. Barry; Andrews, Rosalia N.; Gowens, Terrell F.

1988-01-01

367

Phonon-Assisted Auger Recombination in Gallium Arsenide and Gallium Nitride from First Principles  

NASA Astrophysics Data System (ADS)

GaN and GaAs and their alloys are technologically important materials for solid-state optoelectronic devices such as light emitting diodes. The internal quantum efficiency of these devices, defined as the fraction of electron-hole pairs converted to photons, is limited by non-radiative loss mechanisms. Auger recombination is such a mechanism which decreases the efficiency at high current densities. In this process, the energy and momentum of an electron-hole pair is transferred to a third carrier. Numerically it is found that this process does not lead to relevant loss rates. However, if a phonon is emitted or absorbed at the same time, Auger loss rates increase by several orders of magnitude. We calculate the Auger recombination rate coefficients from first principles using density functional theory. Treating also the phonons from first principles allows us to analyze which modes and wave vectors contribute predominantly to Auger recombination and the non-radiative loss in these materials.

Steiauf, Daniel; Kioupakis, Emmanouil; van de Walle, Chris G.

2013-03-01

368

Preparation of gallium oxynitride powder and its nanofibers by the nitridation of a gallium oxide precursor doped with nickel or cobalt obtained via the citrate route.  

PubMed

Acicular crystals were grown in gallium oxynitride powder prepared by ammonia nitridation of amorphous gallium oxide precursors containing less than 5 at% of either Ni or Co, via the citrate route. The crystals were several tens of nanometres wide, several micrometres long, and grown in the temperature range 750 to 850 degrees C in a flow of ammonia of less than 200 mL min(-1). The crystal structure of the gallium oxynitride was a highly disordered 2H wurtzite-type with some 3C zinc blende-type stacking faults. The crystals grew in their basal plane changing their aspect ratio with the supplying method of small amounts of Ni or Co and an amount of residual carbon. The acicular crystals were grown by the catalytic behavior of Ni or Co to enhance one-dimensional growth in the hexagonal c-plane. PMID:20571651

Miyaake, A; Masubuchi, Y; Takeda, T; Motohashi, T; Kikkawa, S

2010-07-14

369

Study of liquid gallium at high pressure using synchrotron x-ray  

NASA Astrophysics Data System (ADS)

Liquid gallium has been studied at high pressure up to 2 GPa and ambient temperature in a diamond anvil cell using high energy synchrotron x-ray beam. The total x-ray scattering data of liquid gallium were collected up to Q = 12 A?-1 and analyzed using pair distribution functions (PDF). The results indicate that the first nearest neighbor peak and second nearest neighbor (shoulder) peak of PDF in liquid gallium does not change with pressure, whereas the higher order (i.e., third and fourth) nearest neighbor peaks shift towards shorter distance with increasing pressure. Reverse Monte Carlo modeling based on the observed data shows that the coordination number in the liquid gallium increases with pressure from 10.5 at 0.3 GPa to 11.6 at 2 GPa. An atomic arrangement similar to the crystalline phase of Ga(II) with coordination number of 12 is proposed for the locally dense-packed rigid unit in liquid gallium. The volume compression data derived from the structure modeling yield a bulk modulus of 12.1(6) GPa for liquid gallium.

Yu, Tony; Chen, Jiuhua; Ehm, Lars; Huang, Shu; Guo, Quanzhong; Luo, Sheng-Nian; Parise, John

2012-06-01

370

Early recognition of recurrent hepatocellular carcinoma utilizing gallium-67 citrate scintigraphy  

SciTech Connect

Gallium-67 scintigraphy is a valuable test together with other screening tests such as alpha feto-protein (AFP) and other imaging modalities in following up recurrent hepatocellular carcinoma (HCC). Three patients were followed in our institution for intervals varying from 2-24 mo after successful resection of uninodular localized hepatomas. In the first patient, gallium scan showed abnormal localized activity while the computed tomography (CT) scan and the magnetic resonance imaging were negative. Liver function tests and AFP were also normal and the patient was operated upon only on the basis of the gallium scan. The second patient had a follow-up gallium scan 2 mo after the first operation that showed an area of increased activity along the inferior aspect of the right lobe. A CT scan done after that showed no evidence of recurrence, but subsequently became positive when repeated 4 mo later. The third patient had abnormal simultaneous gallium scan and CT scan demonstrating a recurrence in the left adrenal gland while both AFP and carcinoembryonic antigen were normal. This has led us to consider every patient a candidate for a baseline and follow-up gallium scan for evaluation for recurrence following HCC.

Serafini, A.N.; Jeffers, L.J.; Reddy, K.R.; Heiba, S.; Schiff, E.R.

1988-05-01

371

Immunosuppressive therapy in patients with congestive cardiomyopathy and myocardial uptake of gallium-67  

SciTech Connect

Thirty-nine patients with idiopathic congestive cardiomyopathy underwent gallium-67 scintigraphy. Twenty had no evidence of myocardial uptake (group I) and 19 had demonstrable myocardial gallium-67 activity (group II). There was no significant difference in age, sex, duration of symptoms, antecedent viral illness, left ventricular end-diastolic pressure, pulmonary artery systolic pressure, or ejection fraction between the two groups. Fifteen patients in group II were treated with prednisone and azathioprine for a minimum of 8 months. Nine of 15 patients were clinically unchanged and gallium-67 scans remained positive (group IIa). Six patients had significant improvement and resolution of myocardial gallium-67 uptake (group IIb). The mean change in ejection fraction was +0.2% in group I, -4.8% in Group IIa, and +13.8% in group IIb. There were five deaths in group I (25% mortality), three in group IIa (33% mortality), and no deaths in group IIb. The only significant difference between patients in group IIa and those in group IIb was a greater left ventricular posterior wall thickness in group IIa patients. Twenty control patients without cardiac disease had negative gallium-67 scans. We conclude that gallium-67 myocardial scintigraphy may be a useful test for predicting the response to prednisone and azathioprine therapy.

O'Connell, J.B.; Robinson, J.A.; Henkin, R.E.; Gunnar, R.M.

1981-10-01

372

Immunosuppressive therapy in patients with congestive cardiomyopathy and myocardial uptake of Gallium-67  

SciTech Connect

Thirty-nine patients with idiopathic congestive cardiomyopathy underwent gallium-67 scintigraphy. Twenty had no evidence of myocardial uptake (group I) and 19 had demonstrable myocardial gallium-67 activity (group II). There was no significant difference in age, sex, duration of symptoms, antecedent viral illness, left ventricular end-diastolic pressure, pulmonary artery systolic pressure, or ejection fraction between the two groups. Fifteen patients in group II were treated with prednisone and azathioprine for a minimum of 8 months. Nine of 15 patients were clinically unchanged and gallium-67 scans remained positive (group IIa). Six patients had significant improvement and resolution of myocardial gallium-67 uptake (group IIb). The mean change in ejection fraction was +0.2% in group I, -4.8% in Group IIa, and +13.8% in group IIb. There were five deaths in group I (25% mortality), three in group IIa (33% mortality), and no deaths in group IIb. The only significant difference between patients in group IIa and those in group IIb was a greater left ventricular posterior wall thickness in group IIa patients. Twenty control patients without cardiac disease had negative gallium-67 scans. We conclude that gallium-67 myocardial scintigraphy may be a useful test for predicting the response to prednisone and azathioprine therapy.

O'Connell, J.B.; Robinson, J.A.; Henkin, R.E.; Gunnar, R.M.

1981-10-01

373

High-Temperature Decomposition of Brønsted Acid Sites in Gallium-Substituted Zeolites  

SciTech Connect

The dehydroxylation of Broensted acid sites (BAS) in Ga-substituted zeolites was investigated at temperatures up to 850 C using X-ray absorption spectroscopy (XAS), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry-temperature programmed desorption (MS-TPD). X-ray absorption near-edge spectroscopy (XANES) revealed that the majority of gallium has tetrahedral coordination even after complete dehydroxylation. The interatomic gallium-oxygen distance and gallium coordination number determined by extended X-ray absorption fine structure (EXAFS) are consistent with gallium in tetrahedral coordination at low T (< 550 C). Upon heating Ga-Beta and Ga-ZSM5 to 850 C, analysis of the EXAFS showed that 70 and 80% of the gallium was still in tetrahedral coordination. The remainder of the gallium was found to be in octahedral coordination. No trigonal Ga atoms were observed. FTIR measurements carried out at similar temperatures show that the intensity of the OH vibration due to BAS has been eliminated. MS-TPD revealed that hydrogen in addition to water evolved from the samples during dehydroxylation. This shows that dehydrogenation in addition to dehydration is a mechanism that contributes to BAS decomposition. Dehydrogenation was further confirmed by exposing the sample to hydrogen to regenerate some of the BAS as monitored by FTIR and MS-TPD.

K Al-majnouni; N Hould; W Lonergan; D Vlachos; R Lobo

2011-12-31

374

Study of liquid gallium at high pressure using synchrotron x-ray  

SciTech Connect

Liquid gallium has been studied at high pressure up to 2 GPa and ambient temperature in a diamond anvil cell using high energy synchrotron x-ray beam. The total x-ray scattering data of liquid gallium were collected up to Q = 12 A{sup -1} and analyzed using pair distribution functions (PDF). The results indicate that the first nearest neighbor peak and second nearest neighbor (shoulder) peak of PDF in liquid gallium does not change with pressure, whereas the higher order (i.e., third and fourth) nearest neighbor peaks shift towards shorter distance with increasing pressure. Reverse Monte Carlo modeling based on the observed data shows that the coordination number in the liquid gallium increases with pressure from 10.5 at 0.3 GPa to 11.6 at 2 GPa. An atomic arrangement similar to the crystalline phase of Ga(II) with coordination number of 12 is proposed for the locally dense-packed rigid unit in liquid gallium. The volume compression data derived from the structure modeling yield a bulk modulus of 12.1(6) GPa for liquid gallium.

Yu, Tony; Guo Quanzhong; Parise, John [Department of Geosciences, Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); Chen Jiuhua [Department of Geosciences, Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); Department of Mechanical and Materials Engineering, Center for the Study of Matters at Extreme Conditions, Florida International University, Miami, Florida 33199 (United States); Ehm, Lars [Department of Geosciences, Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Huang Shu [Department of Mechanical and Materials Engineering, Center for the Study of Matters at Extreme Conditions, Florida International University, Miami, Florida 33199 (United States); Luo Shengnian [Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-06-01

375

Fabrication and properties of gallium phosphide variable colour displays  

NASA Technical Reports Server (NTRS)

The unique properties of single-junction gallium phosphide devices incorporating both red and green radiative recombination centers were investigated in application to the fabrication of monolithic 5 x 7 displays capable of displaying symbolic and alphanumeric information in a multicolor format. A number of potentially suitable material preparation techniques were evaluated in terms of both material properties and device performance. Optimum results were obtained for double liquid-phase-epitaxial process in which an open-tube dipping technique was used for n-layer growth and a sealed tipping procedure for subsequent p-layer growth. It was demonstrated that to prepare devices exhibiting a satisfactory range of dominant wavelengths which can be perceived as distinct emission colors extending from the red through green region of the visible spectrum involves a compromise between the material properties necessary for efficient red emission and those considered optimum for efficient green emission.

Effer, D.; Macdonald, R. A.; Macgregor, G. M.; Webb, W. A.; Kennedy, D. I.

1973-01-01

376

Magnetism driven by surface dangling bonds in gallium nitride nanoclusters  

NASA Astrophysics Data System (ADS)

Magnetic properties of gallium nitride (GaN) semiconductor nanoclusters (NCs) of different sizes were systematically studied by using first-principles calculations. It is observed that the pure GaN NCs can be magnetic even without magnetic elements doping. Similar to the observed magnetism in undoped oxide NCs, the magnetism of the undoped GaN NCs is attributed to the spin polarization of the dangling bond electrons of the 2-coordinate surface nitrogen anions and originates from the spatially localized nature of the dangling bond states and associated on-site Hubbard interaction. It is demonstrated that the magnetism driven by the surface dangling bonds can be suppressed or enhanced via hydrogen passivation or structural design. These results indicate that it is promising to combine the surface magnetism of the GaN NCs with their unique optical properties to fabricate nanosized magneto-optical devices.

Zhao, X. G.; Tang, Z.; Hu, W. X.

2013-02-01

377

A model for pore growth in anodically etched gallium phosphide  

NASA Astrophysics Data System (ADS)

The electrochemical etching process of porous gallium phosphide was studied by means of the characteristic current-potential (I-V) curves. Measurements were performed in H2SO4 0.5-M aqueous solution both in the dark and by illuminating the samples with the 351-nm line of an argon laser. Raman spectroscopy was applied to investigate the surface morphology of the samples prepared under different anodizing conditions within the potentiostatic regime. Based on a few reasonable assumptions, a simple model of pore growth is proposed. The enhancing effect in current intensity due to the branching of pores and the opposite effect due to a concomitant decrease in the effective cross area available for carrier transport are accounted for to explain the main features of the recorded I-V curves.

Ricci, P. C.; Salis, M.; Anedda, A.

2005-06-01

378

Experimental study on SPDT machining of Gallium Phosphide  

NASA Astrophysics Data System (ADS)

Gallium Phosphide (GaP) is widely used semiconductor material, but can be also used as a material for visible and infrared optical elements. Combination of its optical and mechanical properties such as high mechanical durability, transparency from visible to infrared wavelengths and high refractive index makes it very interesting material for design of high performance optical systems in NIR and MWIR. Manufacturing of optical elements for such wavelength ranges is shifting from traditional grinding and polishing techniques to a more versatile SPDT machining. It is therefore useful to employ SPDT in production of optical surfaces on GaP. As the GaP is similar to GaAs, but harder and more brittle, all all the problems already known for GaAs are present. Here we report results of experiments with SPDT machining of optical surfaces on GaP substrates and comparison with classical machining methods.

Vaclavík, J.; Dole?ek, R.; Lédl, V.; Psota, P.

2013-09-01

379

Electrical and mechanical properties of vapour grown gallium monotelluride crystals  

NASA Astrophysics Data System (ADS)

The physical vapour deposition (PVD) of gallium monotelluride (GaTe) in different crystalline habits was established in the growth ampoule, strongly depending on the temperature gradient. Proper control on the temperatures of source and growth zones in an indigenously fabricated dual zone furnace could yield the crystals in the form of whiskers and spherulites. Optical and electron microscopic images were examined to predict the growth mechanism of morphologies. The structural parameters of the grown spherulites were determined by X-ray powder diffraction (XRD). The stoichiometric composition of these crystals was confirmed using energy dispersive analysis by X-rays (EDAX). The type and nature of electrical conductivity were identified by the conventional hot probe and two probe methods, respectively. The mechanical parameters, such as Vickers microhardness, work hardening index, and yield strength, were deduced from microindentation measurements. The results show that the vapour grown p-GaTe crystals exhibit novel physical properties, which make them suitable for device applications.

Reshmi, P. M.; Kunjomana, A. G.; Chandrasekharan, K. A.

2013-10-01

380

Spectroscopic ellipsometric studies of randomly distributed plasmonic Gallium nanoparticles  

NASA Astrophysics Data System (ADS)

Ultraviolet surfaced-enhanced Raman scattering (UV-SERS) was recently observed using randomly distributed Gallium nanoparticles (Ga NPs) deposited on sapphire by molecular beam expitaxy at room temperature. Atomic force and scanning electron microscopies revealed that the radii of the hemispheroid NPs follow unimodal or bimodal pseudo Gaussian distributions whose mean diameters increase with increasing Ga dosage (i.e. growth time). Variable angle spectroscopic ellipsometric measurements were then performed on Ga NP ensembles to explore the correlation between the polarimetric optical response and the local morphology. An effective medium composed of single or double Lorentzian oscillators was found to reproduce the optical response of Ga NP ensembles with resonance frequencies that decrease monotonically with increasing NP size. In addition, a strong depolarization response was observed for near-normal incidence. Interestingly, the sample for which the depolarization peak was closest to the 325nm laser excitation wavelength was the sample with the highest SERS enhancement factor.

Yang, Yang; Kim, Tong-Ho; Akozbek, Neset; Brown, April; Everitt, Henry

2013-03-01

381

Results from the Soviet-American gallium experiment  

SciTech Connect

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of {sup 71}Ge atoms extracted from thirty tons of gallium was measured in five runs during the period of January to July 1990. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20 + 15/{minus}20 (stat) {plus_minus} 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model.

Abazov, A.I.; Anosov, O.L.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.V.; Pshukov, A.M.; Revzin, N.E.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zatsepin, G.T. [AN SSSR, Moscow (USSR). Inst. Yadernykh Issledovanij; Bowles, T.J.; Cleveland, B.T.; Elliott, S.R.; O`Brien, H.A.; Wark, D.L.; Wilkerson, J.F. [Los Alamos National Lab., NM (United States); Davis, R. Jr.; Lande, K. [Pennsylvania Univ., Philadelphia, PA (United States); Cherry, M.L. [Louisiana State Univ., Baton Rouge, LA (United States); Kouzes, R.T. [Princeton Univ., NJ (United States)

1991-12-31

382

Results from the Soviet-American gallium experiment  

SciTech Connect

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of {sup 71}Ge atoms extracted from thirty tons of gallium was measured in five runs during the period of January to July 1990. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20 + 15/{minus}20 (stat) {plus minus} 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model.

Abazov, A.I.; Anosov, O.L.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.V.; Pshukov, A.M.; Revzin, N.E.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zatsepin, G.T. (AN SSSR, Moscow (USSR). Inst. Yadernykh Issledovanij); Bowles, T.J.; Cleveland, B.T.; Elliott, S.R.; O'Brien, H.A.; Wark, D.L.; Wilkerson, J.F.

1991-01-01

383

Coated gallium arsenide neutron detectors : results of characterizationmeasurements.  

SciTech Connect

Effective detection of special nuclear materials (SNM) is essential for reducing the threat associated with stolen or improvised nuclear devices. Passive radiation detection technologies are primarily based on gamma-ray detection and subsequent isotope identification or neutron detection (specific to neutron sources and SNM). One major effort supported by the Department of Homeland Security in the area of advanced passive detection is handheld or portable neutron detectors for search and localization tasks in emergency response and interdiction settings. A successful SNM search detector will not only be able to confirm the presence of fissionable materials but also establish the location of the source in as short of time as possible while trying to minimize false alarms due to varying background or naturally occurring radioactive materials (NORM). For instruments based on neutron detectors, this translates to detecting neutrons from spontaneous fission or alpha-n reactions and being able to determine the direction of the source (or localizing the source through subsequent measurements). Polyethylene-coated gallium arsenide detectors were studied because the detection scheme is based on measuring the signal in the gallium arsenide wafers from the electrical charge of the recoil protons produced from the scattering of neutrons from the hydrogen nucleus. The inherent reaction has a directional dependence because the neutron and hydrogen nucleus have equivalent masses. The assessment and measurement of polyethylene-coated gallium arsenide detector properties and characteristics was the first phase of a project being performed for the Department of Homeland Security and the results of these tests are reported in this report. The ultimate goal of the project was to develop a man-portable neutron detection system that has the ability to determine the direction of the source from the detector. The efficiency of GaAs detectors for different sizes of polyethylene layers and different angles between the detector and the neutron source were determined. Preliminary measurements with a neutron generator based on a deuterium-tritium reaction ({approx}14 MeV neutrons) were performed and the results are discussed. This report presents the results of these measurements in terms of efficiency and angular efficiency and compares them to Monte Carlo calculations to validate the calculation scheme in view of further applications. Based on the results of this study, the polyethylene-coated gallium arsenide detectors provide adequate angular resolution based on proton recoil detection from the neutron scattering reaction from hydrogen. However, the intrinsic efficiency for an individual detector is extremely low. Because of this low efficiency, large surface area detectors ( or a large total surface area from many small detectors) would be required to generate adequate statistics to perform directional detection in near-real time. Large surface areas could be created by stacking the detector wafers with only a negligible attenuation of source neutrons. However, the cost of creating such a large array of GaAs is cost-prohibitive at this time.

Klann, R. T.; Perret, G.; Sanders, J.

2006-09-29

384

High efficient organic ultraviolet photovoltaic devices based on gallium complex  

NASA Astrophysics Data System (ADS)

High efficient organic ultraviolet (UV) photovoltaic devices comprising 4,4',4?-tri-(2-methylphenyl phenylamino) triphenylamine (m-MTDATA) and tris-(8-hydroxyquinoline) gallium (Gaq 3) as the electron donor and acceptor, respectively, are demonstrated. The m-MTDATA/Gaq 3 bilayer device shows a short-circuit current density of 59.3 ?A/cm 2, a open-circuit voltage of 1.85 V, a fill factor of 0.41, and a power conversion efficiency of 3.74% under illumination of a 1.2 mW/cm 2 365 nm UV light. And this power conversion efficiency is superior than that of the device based on tris-(8-hydroxyquinoline) aluminum with the same device structure, which is attributed to the high electron mobility of Gaq 3 and the low exciton loss via radiation decay and hence more exciton dissociation in m-MTDATA/Gaq 3 device.

Su, Zisheng; Chu, Bei; Li, Wenlian

2010-05-01

385

Design and Performance Estimates of an Ablative Gallium Electromagnetic Thruster  

NASA Technical Reports Server (NTRS)

The present study details the high-power condensable propellant research being conducted at NASA Glenn Research Center. The gallium electromagnetic thruster is an ablative coaxial accelerator designed to operate at arc discharge currents in the range of 10-25 kA. The thruster is driven by a four-parallel line pulse forming network capable of producing a 250 microsec pulse with a 60 kA amplitude. A torsional-type thrust stand is used to measure the impulse of a coaxial GEM thruster. Tests are conducted in a vacuum chamber 1.5 m in diameter and 4.5 m long with a background pressure of 2 microtorr. Electromagnetic scaling calculations predict a thruster efficiency of 50% at a specific impulse of 2800 seconds.

Thomas, Robert E.

2012-01-01

386

Kinetically controlled growth of gallium on stepped Si (553) surface  

NASA Astrophysics Data System (ADS)

Kinetically controlled growth of gallium (Ga) metal has been reported on high index stepped Si (553) surface and its thermal stability with various novel superstructural phases has been analyzed. Auger electron spectroscopy studies revealed that the adsorption of Ga at room temperature (RT) follows Frank-van der Merwe (FM) growth mode while for higher substrate temperature, Ga adsorption remains within the submonolayer range. Thermal desorption and low energy electron diffraction studies investigated the formation of thermally stable Ga-islands and the various Ga induced superstructural phase on Si (553). During room temperature adsorption, (1 1 1)7 × 7 facet of Si (553) reconstructed into (1 1 1)6 × 6 facet while during desorption process, stable (1 1 1)6 × 6 and (1 1 1)?3 × ?3-R30° surface reconstructions has been observed.

Kumar, Mukesh; Pasha, Syed Khalid; Govind

2013-10-01

387

Investigation of Gadolinium Gallium Oxide using spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Spectroscopic Ellipsometry (SE) is a non-destructive characterization technique used for determining film thickness, interfacial roughness and optical properties of single and multilayered materials. SE measures the change in the polarization state of the incident light upon reflection from these layers providing insight into the properties and composition of topmost and underlying materials. The Horiba Jobin Yvon - UVISEL located in the Angelo State Materials Characterization Lab is based on the principle of phase modulated spectroscopic ellipsometry. This tool has been used to successfully characterize a variety of semiconductor samples. We will detail results from semiconductor heterostructures containing Gadolinium Gallium Oxide (GdGaO3), a novel material with promise for application as a high-k dielectric in the design of compound semiconductor MOSFETs. Models for this unusual material have been developed and used to characterize various structures with success. We have obtained reasonable values for electrical and optical parameters for the GGO not found in current literature.

Bhatnagar, Kunal; Sauncy, Toni; Droopad, Ravi

2010-03-01

388

A dicationic gallium-oxo-hydroxide cage compound  

PubMed

The crystal structure of hexa-&mgr;-hydroxo-dodecamethylocta-&mgr;(3)-oxo-dodecagallium(III) bis[tetrakis(pentafluorophenyl)borate(III)] chlorobenzene disolvate dihydrate, [Ga(12)(CH(3))(12)(&mgr;(3)-O)(8)(&mgr;-OH)(6)](C(24)F(20)B)(2). 2C(6)H(5)Cl.2H(2)O, is reported. The gallium-oxo-hydroxide dication is located on an inversion center and adopts a cage structure composed of 12 fused Ga(3)O(3) rings and is associated with the hydrate molecules and the [B(C(6)F(5))(4)](-) anions through hydrogen bonds and one O-H.pi-ring interaction. Disordered chlorobenzene solvent molecules are also present in the crystal structure. PMID:11025300

Swenson; Dagorne; Jordan

2000-10-01

389

Near-electrode processes in lanthanum-gallium tantalate crystals  

SciTech Connect

The near-electrode processes on the surfaces of the polar cuts of lanthanum-gallium tantalate crystals grown in different atmospheres were investigated. The temperature dependences of short-circuit currents in the temperature range 20-700{sup o}C were measured and phase analysis of the sample surfaces after the temperature tests were performed. It is shown that short-circuit currents arise on the surfaces of polar cuts with identical conducting coatings without preliminary polarization. These currents are caused by the generation of intrinsic emf as a result of the electrochemical reactions on opposite polar cut surfaces coming in contact with a conducting coating. It is established that the crystal growth atmosphere and the conducting coating material significantly affect the temperature dependences of short-circuit currents.

Buzanov, O. A. [OAO Fomos Materials (Russian Federation); Zabelina, E. V., E-mail: e.zabelina@gmail.com; Kozlova, N. S., E-mail: kozlova_nina@mail.ru; Sagalova, T. B. [Moscow State Institute of Steel and Alloys (Russian Federation)

2008-09-15

390

Synthesis and characterization of electrospun gallium nitride nanofibers  

NASA Astrophysics Data System (ADS)

The simple and inexpensive technique of electrospinning was used for the production of long GaN nanofibers. The fibers were made using a precursor solution composed of pure Gallium Nitrate dissolved in dimethylacetamide (DMA) and a viscous solution of Cellulose acetate dissolved in a mixture of DMA and acetone. Using a tube furnace, they were sintered under a Nitrogen atmosphere to decompose the polymer and to reduce Oxygen contamination. This process was followed by sintering under a NH3 flow to complete the synthesis of wurtzite GaN. XRD, ESEM, and FTIR analysis were used to verify the chemical and structural composition of the samples. The I-V characteristics of a device constructed using a single GaN nanofiber showed the formation of ohmic contacts.

Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago-Avilés, Jorge J.

2009-08-01

391

Biomineralization of uniform gallium oxide rods with cellular compatibility.  

PubMed

Monodispersed single crystalline alpha-GaOOH rods coated by silk fibroin (SF) have been prepared via a facile biomineralization process in the template of SF peptide. The carbon-coated alpha-Ga(2)O(3) and beta-Ga(2)O(3) rods are obtained by thermal treatment of the alpha-GaOOH rods at 600 and 800 degrees C, respectively. In vitro cytotoxicity studies of these gallium oxide rods showed no significant effect leading to restraint of cell proliferation of L929, Hela, and HaCat cells in less than 0.1 mg/mL prepared rods. On the basis of their excellent luminescence emission properties and cellular compatibilities, possible applications for bio-optoelectronic devices can be envisioned. PMID:19537684

Yan, Danhong; Yin, Guangfu; Huang, Zhongbing; Liao, Xiaoming; Kang, Yunqing; Yao, Yadong; Hao, Baoqing; Gu, Jianwen; Han, Dong

2009-07-20

392

The Use of the Gallium Triple Point in Platinum Resistance Thermometer Interpolation below 273.15 K  

NASA Astrophysics Data System (ADS)

The effect of replacing the boiling point of water with the triple point of gallium in several interpolation schemes for platinum resistance thermometers below 273.15 K is investigated. The sensitivity of the schemes to calibration errors in the gallium point is about five times higher than for calibration errors in the boiling point of water. This disadvantage is offset, however, by the greater accuracy of realization of the gallium point.

Kemp, R. C.

1987-01-01

393

Gallium phosphinoarylbisthiolato complexes counteract drug resistance of cancer cells.  

PubMed

In cancer therapy the platinum-based drugs are used frequently with a good clinical outcome, but besides unwanted side effects which occur, the tumour cells subjected to treatment are prone to develop tolerance or even multidrug resistance (MDR). Metal compounds with a central atom other than platinum are efficient in targeting the chemoresistant cells, therefore the biological outcome of two recently synthesized gallium phosphinoarylbisthiolato complexes was studied, having the formula [X][Ga{PPh(2-SC6H4)2-?(3)S,S',P}{PPh(2-SC6H4)2-?(2)S,S'}] where [X] is either the NEt3H (1) or PPh4 (2) cation. Compounds 1 and 2 display in vitro cytotoxicity against both platinum-sensitive and platinum-resistant cell lines (A2780 and A2780cis). Morphological and ultrastructural evidence points toward their capacity to impair tumour cells survival. This behaviour is based on malignant cells capacity to selectively intake gallium, and to bind to the cellular DNA. They are able to cause massive DNA damage in treated cancer cells, focusing on 7-methylguanine and 8-oxoguanine sites and oxidizing the pyrimidine bases; this leads to early apoptosis of a significant percent of treated cells. The intrinsic and extrinsic apoptotic pathways are influenced through the modulation of gene expression following the treatment with complexes 1 and 2, which accompanies the negative regulation of P-glycoprotein 1 (Pgp-1), an important cellular ABC-type transporter from the multidrug resistance (MDR) family. The studied Ga(III) compounds demonstrated the capacity to counteract the chemoresistance mechanisms in the tumours defiant to standard drug action. Compound 2 shows a good anticancer potential and it could represent an alternative to platinum-based drugs especially in the situation of standard treatment failure. PMID:24413432

Fischer-Fodor, Eva; V?lean, Ana-Maria; Virag, Piroska; Ilea, Petru; Tatomir, Corina; Imre-Lucaci, Florica; Schrepler, Maria Perde; Krausz, Ludovic Tibor; Tudoran, Lucian Barbu; Precup, Calin George; Lupan, Iulia; Hey-Hawkins, Evamarie; Silaghi-Dumitrescu, Luminita

2014-04-01

394

Molecular dynamics simulations of adhesion and nanoindentation of gallium arsenide  

NASA Astrophysics Data System (ADS)

The purpose of this dissertation is to investigate the nanoscale hardness of gallium arsenide thin films and the elastic-plastic behavior of gallium arsenide under an indenter. These investigations were carried out using molecular dynamics (MD) simulations. The simulations are based on interatomic potentials that accurately reproduce many properties of bulk GaAs. The MD simulations performed required scalable and efficient algorithms for implementation on large parallel computers. Nanoindentation simulations were performed using an ideal indenter that was held rigid during the simulation. To reduce the transient effects due to loading, the traversal of the indenter was interrupted periodically to allow the substrate to relax. Load-displacement curves were calculated and Vickers hardness and Young's modulus were computed from the curves. The damage caused by the indenter was characterized in three ways. The material deposited on the surface was compared to bulk amorphous GaAs and found to be structurally similar, indicating that the material underwent solid-state amorphization under the indenter. Analysis of energetic atoms beneath the surface suggested the presence of dislocation loops. A centrosymmetry method was applied to characterize these defects. It was found that the method used did not perform adequately in the presence of amorphized material. Pressure distributions were calculated and atomic configurations were plotted to determine if subsurface microcracking due to the indentation was present. No indication of microcracking or pore formation was found. Adhesion between the tip and substrate was also studied. The effect of the tip-surface attraction was studied for a modified Vickers indenter with a small flat surface instead of an atomically sharp tip. For indentations less than the yield point in GaAs, the bond formation between the tip and the surface led to nonelastic deformation of the surface layer, while the layers underneath the surface behaved in a purely elastic fashion. Through a series of small indenter traversals, the yield point of GaAs was determined to be 0.6 muN.

Neal, Francis Brent, Jr.

2002-01-01

395

Optical characterization of gallium nitride and zinc oxide  

NASA Astrophysics Data System (ADS)

The optical properties of Gallium Nitride (GaN) and Zinc Oxide (ZnO) were studied through transmission spectroscopy and photoluminescence. The use of very thin films of less than 0.5 ?m on a transparent sapphire substrate permitted the direct observation of excitons at room temperature and 77 K in both materials. The films used were thin enough that the absorption coefficient was accurately determined above the band gap. The excitonic structure observed was fit with an excitonic model of absorption determining the exciton binding energy, band gaps and valence band splittings. In the case of gallium nitride the recombination constant was also determined. In photoluminescence studies of a bulk single crystal ZnO, line narrowing and modal development was observed indicative of stimulated emission and lasing. The photoluminescence of ZnO nanoparticles was also studied and found to be comparable to the luminescence of single crystal ZnO. Single crystal epitaxial ZnO thin films were deposited by pulsed laser deposition. The as-deposited films were of high quality, but it was found that annealing the films in oxygen could remove the point defects improving the films further. The improvement in the films was quantified through observation of the excitonic structure. It was also found that annealing improved band edge luminescence significantly and reduced defect luminescence. In photoluminescence studies of polycrystalline ZnO films deposited by sputtering on quartz substrates, it was found that ultraviolet laser light can be used to anneal the ZnO. The unannealed portions of the sample did not emit light while the annealed portions emitted light efficiently. Changes in the film morphology were also observed.

Muth, John Franklyn

1998-09-01

396

Gallium Arsenide Thin Films on Tungsten/Graphite Substrates: Phase II. Quarterly Project Report No. 1, September 1, 1977--November 30, 1977.  

National Technical Information Service (NTIS)

Efforts have been directed to the deposition and characterization of gallium arsenide films on graphite and tungsten/graphite substrates and the fabrication and evaluation of solar cells on these substrates. Sulfur doped gallium arsenide films have been d...

S. S. Chu

1977-01-01

397

Study of palladium/gallium antimonide reactions and ohmic contacts to N-type gallium antimonide  

NASA Astrophysics Data System (ADS)

Antimonide-based compound semiconductors show great promise for optoelectronic and high speed electronic devices. GaSb, and related ternary and quaternary alloys, have emerged as critical materials for infrared lasers, thermophotovoltaic devices, solar cells, and transistors. To ensure device reliability and performance, ohmic contacts with low specific contact resistance, good thermal stability, and excellent surface and interfacial morphology are required. In recent years a move from traditional Au-based contacts to Pd-based contacts has improved thermal and morphological stability of contacts to Sb-based semiconductors. The characterization and understanding of how a Pd thin film interacts with GaSb is essential to further improve contacts to n-GaSb. Research presented in this thesis yields phase formation and reaction morphologies important for Pd-based contacts to n-GaSb. A Pd/GaSb thin film study identifies phase formation necessary for the solid phase regrowth mechanism for ohmic contact formation and the ohmic behavior of a Pd (50 nm)/GaSb contact. A subsequent study of the Pd-rich region of the Pd-Ga-Sb phase diagram verifies the existence of several Pd-rich ternary phases observed in the thin film research. Next, research focused on the engineering of Pd-bearing ohmic contacts that include indium. Two low resistance ohmic contacts will be presented that exhibit electrical properties comparable to In-based contacts reported in the literature. However, these contacts improve upon previously reported contacts to n-GaSb by offering improved surface morphology, reduced reaction depth, and improved thermal stability. A Pd3In7/WSiN/Au contact presented here exhibits unmatched thermal stability and ultra-shallow reaction depths. Finally, the effect of surface treatments will be presented as a means to reduce the specific contact resistance, improve reaction uniformity, and understand Sb-based semiconductor passivation. It will be shown that by replacing a conventional surface treatment that includes a deionized water rinse with a dilute ammonium sulfide solution rinse, it is possible to rid the surface of any contamination layers, reduce the specific contact resistance of ohmic contacts to n-GaSb, and improve reaction uniformity.

Robinson, Joshua Alexander

398

Sites of tuberculous involvement in patients with AIDS. Autopsy findings and evaluation of gallium imaging.  

PubMed

The purpose of this study was to review autopsy and gallium scan findings in two different acquired immune deficiency syndrome (AIDS) patient populations who had a confirmed diagnosis of tuberculosis (TB) to identify organs involved and accuracy of clinical diagnosis. The first group was comprised of 29 autopsies between January 1982 and December 1994, including only 18 patients who were diagnosed before death. Organs most commonly involved were the lymph nodes (59%), lungs (56%), spleen (53%), liver (45%), and kidneys (37%). Other opportunistic infections were present in 18 (59%) of autopsies, with more than one opportunistic infection present in 11 (37%) of the autopsies. Lungs were involved in 79% of all autopsies. The second population group included 94 patients with AIDS with a proven diagnosis of TB, only 24 of whom had gallium scans in the period between January 1992 and December 1994. Chest x-ray results were negative in 4 patients (17%); gallium scan results were positive in 16 patients (66%). The reasons for false-negative gallium scan results were due to anti-tuberculous treatment for periods varying from 2-21 months in 7 patients or the presence of extra pulmonary tuberculosis. The sites of TB involvement in the chest were: lung parenchyma in 5 patients (19%, 4 in mid and lower lung, and 1 in upper fields). There was lymph node involvement in all 16 patients (24 locations with mediastinal involvement in 23%, supraclavicular 23%, axillary 11%, retroperitoneal 11%, and inguinal region in 4%. We conclude that (1) tuberculosis in patients with AIDS behaves similar to primary tuberculosis; (2) the combination of chest x-ray and gallium imaging is sensitive for the diagnosis of pulmonary tuberculosis in patients with AIDS; (3) the involvement of mediastinal lymph nodes in gallium scans in the presence or absence of chest x-ray abnormalities should raise the possibility of TB involvement in patients with human immunodeficiency virus; (4) anti-TB treatment decreases the sensitivity of gallium scan. PMID:9152531

Abdel-Dayem, H M; Naddaf, S; Aziz, M; Mina, B; Turoglu, T; Akisik, M F; Omar, W S; DiFabrizio, L; LaBombardi, V; Kempf, J S

1997-05-01

399

Changes in the temperatures of phase transformations of the Ni2MnGa alloy upon substitution of nickel for manganese  

NASA Astrophysics Data System (ADS)

Temperatures of phase transformations of a number of Ni2MnGa-based alloys (four compositions), which are characterized by substitution of nickel for manganese at an unchanged gallium content (25 at %), have been determined. As the nickel concentration increases with respect to the stoichiometric composition (or the electron concentration e/ a increases), the liquidus ( T liq), solidus ( T sol), and martensitic transformation ( T mart) temperatures increase, whereas the magnetic transformation temperature ( T C) decreases slightly.

Stepanova, N. N.; Rodionov, D. P.; Kazantsev, V. A.; Sazonova, V. A.; Akshentsev, Yu. N.

2007-12-01

400

Lattice Parameter Variation in ScGaN Alloy Thin Films on MgO(001) Grown by RF Plasma Molecular Beam Epitaxy  

Microsoft Academic Search

We present the structural and surface characterization of the alloy formation of scandium gallium nitride ScxGa1-xN(001)\\/MgO(001) grown by radio-frequency molecular beam epitaxy over the Sc range of x = 0-100%. In-plane diffraction measurements show a clear face-centered cubic surface structure with single-crystalline epitaxial type of growth mode for all x; a diffuse\\/distinct transition in the surface structure occurs at near

Arthur Smith; Costel Constantin; Jeongihm Pak; Kangkang Wang; Abhijit Chinchore; Meng Shi

2010-01-01

401

Alloy softening in binary molybdenum alloys  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

Stephens, J. R.; Witzke, W. R.

1972-01-01

402

Preparation and lithium doping of gallium oxynitride by ammonia nitridation via a citrate precursor route  

SciTech Connect

Gallium oxynitride, isostructural to hexagonal gallium nitride (h-GaN), was obtained by ammonia nitridation of a precursor prepared from the addition of citric acid to an aqueous solution of gallium nitrate. Gallium oxynitride produced at 750 deg. C had a small amount of gallium vacancies, and was formulated as (Ga{sub 0.89}{open_square}{sub 0.11}) (N{sub 0.66}O{sub 0.34}) where the symbol {open_square} stands for gallium vacancy. Both the gallium vacancies and oxygen substituted for nitrogen were randomly distributed within the structure. The amount of vacancies decreased with nitridation temperatures in the range of 750-850 deg. C. Approximately, 10 at% Li{sup +} was doped into the gallium oxynitride, using a similar preparation with the additional presence of lithium nitrate, resulted in the random substitution of Ga{sup 3+} in an atomic ratio of Li/Ga<1 at 750 deg. C. Oxygen was codoped with lithium and substituted nitrogen in the wurtzite-type crystal lattice. These substitutions reduced the electrical conductivity in the gallium oxynitride semiconductor. A new oxynitride, Li{sub 2}Ga{sub 3}NO{sub 4}, was also obtained with Li{sub 2}CN{sub 2} impurity using similar preparations from a mixture of Li/Ga{>=}1. The crystal structure was isostructural with h-GaN, and was refined as P6{sub 3} mc with a=0.31674(1) nm, and c=0.50854(2) nm. The Ga and Li occupancies at the 2b site were refined to be 0.6085 and 0.3915, respectively, assuming that the other 2b site was randomly occupied with 1/5O and 4/5N. When the new compound was washed for over 1 min for the removal of Li{sub 2}CN{sub 2} impurities, it was decomposed to a mixture of {alpha}-GaOOH and {alpha}-LiGaO{sub 2}. The as-prepared product with Li/Ga=1 showed the highest intensity in yellow luminescence among the products under excitation at 254 nm. - Graphical abstract: Schematic gallium vacancy distribution within a Ga-plane in wurtzite-type gallium oxynitride prepared via a citrate precursor route. Closed and open circles represent gallium and its vacancy sites, respectively. This is the most probable case among various kinds of statistical vacancy distribution, where Ga/vacancy=6/1 in atomic ratio. About 10 at% Li{sup +} could be doped to the gallium oxynitride by substituting Ga{sup 3+}. Well-crystallized new oxynitride, Li{sub 2}Ga{sub 3}NO{sub 4}, isostructural with h-GaN, was also obtained in the preparation with Li/Ga{>=}1.

Kikkawa, Shinichi [Graduate School of Engineering, Hokkaido University, N13W8, Kita-ku Sapporo 060-8628 (Japan)], E-mail: kikkawa@eng.hokudai.ac.jp; Nagasaka, Kazuteru [Graduate School of Engineering, Hokkaido University, N13W8, Kita-ku Sapporo 060-8628 (Japan); Takeda, Takashi [Graduate School of Engineering, Hokkaido University, N13W8, Kita-ku Sapporo 060-8628 (Japan); Bailey, Mark [Graduate School of Engineering, Hokkaido University, N13W8, Kita-ku Sapporo 060-8628 (Japan); Sakurai, Toshitaka [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Miyamoto, Yoshinari [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

2007-07-15

403

Synthesis of gallium oxide nanomaterials on source material supply and their growth behavior.  

PubMed

High purity and single crystalline beta-Ga2O3 nanomaterials with various morphologies were obtained through the simple thermal evaporation of metal gallium powder on a gold-coated silicon substrate in argon. In this report, the growth behavior of the beta-Ga2O3 nanomaterials as a function of synthesis time and source material supply was delicately surveyed via FESEM and HRTEM. The synthesis time and source material supply affected morphology, growth rate and growth mechanism of the grown nanomaterials. It was confirmed that the growth mechanism of the beta-Ga2O3 nanomaterials was varied in the order of VLS, combination of VLS and VS, and VS, by increasing the synthesis time without regard to the supply of the source material. When the source materials supply was increased, many beta-Ga2O3 nanomaterials with various morphologies, such as sheet, triangle, and belt-like were appeared. It was confirmed that the oxidation reaction of gallium and oxygen for the formation of gallium oxide nanomaterials carried out the precipitation of gallium at the same time due to the supersaturation of the gallium atoms in gold catalyst. The growth and formation mechanism of the beta-Ga2O3 nanomaterials are discussed herein. PMID:22121682

Cho, Kwon Koo; Sim, Sung Joo; Kim, Hye Sung

2011-07-01

404

Planning mantle radiation therapy in patients with Hodgkin disease: role of gallium-67 scintigraphy  

SciTech Connect

Detection of all sites of lymphoma is imperative for accurate planning of radiation therapy. In patients with Hodgkin disease, mantle radiation is used to treat the thoracic lymph nodes; in those with early-stage or nonbulky disease, mantle and paraaortic radiation may be the only treatment given. CT scanning of the chest adds important information to that obtained from chest radiographs. Gallium-67 scintigraphy has also been used to provide additional information on sites of active tumor. To determine the usefulness of 67Ga-citrate scintigraphy in planning the portals for radiation therapy, we analyzed the radiation treatment plans in 26 consecutive patients with Hodgkin disease; in all 26 patients, the disease had been staged by chest radiographs, chest CT scans, and gallium-67 images. Gallium-67 imaging alone provided unique information that affected the treatment plans in three patients (12%). The combined results of gallium-67 imaging and CT scans influenced the planning of radiation therapy in eight patients (31%). Gallium-67 imaging was found to be an important adjunctive study for optimal planning of radiation therapy in patients with Hodgkin disease.

Jochelson, M.S.; Herman, T.S.; Stomper, P.C.; Mauch, P.M.; Kaplan, W.D.

1988-12-01

405

Cleansing the colon in gallium-67 scintigraphy: a prospective comparison of regimens.  

PubMed

Colonic accumulation of gallium-67 frequently complicates the interpretation of gallium-67 scintigrams. Although various modes of cleansing the colon prior to scintigraphy have been suggested, there is controversy over their efficacy and none have been tested prospectively. Three hundred nine patients undergoing gallium-67 scintigraphy were randomly assigned to one of four cleansing regimens: (1) a high fiber diet (78 patients); (2) castor oil (76); (3) milk of magnesia and cascara (76); and (4) not preparation (79). Patient compliance rates for the four regimens were 17%, 32%, 36%, and 46%, respectively. After noncompliant patients were excluded, gallium-67 scintigrams were graded for colonic activity on a scale of 0-3 by three independent, experienced observers. Gallium-67 activity in the colon was significantly less after administration of castor oil than after no preparation (p = 0.047). A high fiber diet also resulted in a substantial reduction of colonic activity when compared with no preparation; the difference, however, was not statistically significant (p = 0.083). Regimen 3 did not produce significantly better results than regimen 4 (p = 0.42). A major impediment to the success of any cleansing regimen seems to be poor compliance of patients. PMID:6270994

Novetsky, G J; Turner, D A; Ali, A; Raynor, W J; Fordham, E W

1981-11-01

406

(Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon  

DOEpatents

The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Midland, MI)

2001-01-01

407

(Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon  

DOEpatents

The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Midland, MI)

2002-01-01

408

Point Defects, Diffusion Mechanisms, and Superlattice Disordering in Gallium Arsenide-Based Materials. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

This paper reviews recent progresses in our understanding of the mechanisms of Gallium self diffusion and impurity diffusion in GaAs, and of the disordering of GaAs/AlGaAs superlattices. Gallium self diffusion and Al-Ga interdiffusion under intrinsic and ...

T. Y. Tan U. Goesele S. Yu

1991-01-01

409

Additional P(3/2) and P(1/2) Infrared Excited State Lines of Gallium and Indium in Silicon.  

National Technical Information Service (NTIS)

Infrared excitation spectra were measured for the p3/2 lines of gallium in silicon. Two missing lines were observed, and a previous weak or doubtful one was confirmed. Spectra were also obtained of the p1/2 lines of gallium and indium in silicon, demonstr...

J. J. Rome R. J. Spry T. C. Chandler G. J. Brown B. C. Covington

1982-01-01

410

Synthesis and characterization of electrodeposited copper indium selenide and copper (indium, gallium) selenide thin films  

NASA Astrophysics Data System (ADS)

Electrodeposition is a cost effective method for growing polycrystalline thin films which is not limited by substrate/superstrate size and does not require the use of a vacuum. In this research, CuInSe2 and Cu(In,Ga)Se 2 polycrystalline thin films have been synthesized by electrodeposition. Both of these materials have very high absorption coefficients when compared to Si and GaAs, and can have their band gaps adjusted through the control of their stoichiometries. Both CuInSe2 and Cu(In,Ga)Se2 are direct band gap semiconductors with the chalcopyrite crystal structure. Therefore, these materials are important for use in high efficiency photovoltaic solar cells. In an attempt to understand how the composition, morphology and crystallinity depend on electrodeposition conditions, various thin films of CuInSe2 and Cu(In,Ga)Se2 were grown by electrodeposition. These films were then characterized by a number of characterization techniques which include (1) scanning electron microscopy, (2) scanning tunneling microscopy, (3) energy dispersive spectroscopy, (4) X-ray diffraction, and (5) Auger electron spectroscopy. Results based on this research indicate two main conclusions. (1) Modulated or layered films of CuInSe2 can be grown by electrodeposition. Measurements made by Scanning Tunneling Microscopy of cleaved cross sections of the CuInSe2 layered films indicate the successful formation of layers. (2) Cu(In,Ga)Se2 thin films can be electrodeposited by a two-step process with minimal post treatment steps. The process developed here can be done at room temperature. Two electrochemical baths are used, one to electrodeposit a CuGa2 binary alloy, followed by the electrodeposition of a CuInSe2 thin film from another bath. The resulting bilayer film is then annealed in flowing argon at an elevated temperature to form the CIGS compound. Characterization results from measurements made by X-ray diffraction show that the resulting films maintain the basic chalcopyrite structure while the Bragg peaks shift to larger diffraction angles with increasing gallium content in the film. This is evidence to support the successful formation of CIGS films. This data is further corroborated by the energy dispersive spectroscopy and Auger electron spectroscopy data.

Friedfeld, Robert Bonheur

411

Investigation of a Gallium MPD Thruster with an Ablating Cathode  

NASA Technical Reports Server (NTRS)

Arc impedance, exhaust velocity, and plasma probe measurements are presented. The thruster is driven by a 50 microsecond pulse from a 6.2 milliohm pulse forming network, and gallium is supplied to the discharge by evaporation of the cathode. The arc voltage is found to vary linearly with the discharge current with an arc impedance of 6.5 milliohms. Electrostatic probes yield an exhaust velocity that is invariant with the discharge current and has a peak value of 20 kilometers per second, which is in reasonable agreement with the value (16 plus or minus 1 kilometer per second) calculated from the mass bit and discharge current data. Triple probe measurements yield on axis electron temperatures in the range of 0.8-3.8 eV, electron densities in the range of 1.6 x 10(exp 21) to 2.1 x 10(exp 22) per cubic meter, and a divergence half angle of 16 degrees. Measurements within the interelectrode region yield a peak magnetic field of 0.8 T, and the observed radial trends are consistent with an azimuthally symmetric current distribution. A cathode power balance model is coupled with an ablative heat conduction model predicting mass bit values that are within 20% of the experimental values.

Thomas, Robert E.; Burton, Rodney L.; Polzin, Kurt A.

2010-01-01

412

Growth of gallium nitride via iodine vapor phase growth  

NASA Astrophysics Data System (ADS)

Thick layers of gallium nitride have been deposited on 1?m thick MOVPE GaN(0001) thin film substrates using a novel vertical iodine vapor phase epitaxy system. The system features three concentric flow zones that separate the reactant gasses until they reached the substrate. Nitrogen flows through the innermost zone and delivers iodine vapor from an external bubbler to the molten Ga maintained at 1040 °C and GaI to the substrate; high-purity ammonia flows through the outermost zone; and nitrogen flows through the middle zone to prevent reaction between the growth species at the GaI nozzle. Growth rates greater than 75 ?m/hr have been achieved at a V/III ratio of 75. The use of higher V/III ratios resulted in lower growth rates. Optical microscopy of the final growth surfaces revealed spiral hillocks with base diameters as large as 1mm. Increased Ga in the vapor phase resulted in a duplex microstructure containing both hillocks and faceted, oriented crystals overgrowing the hillocks.

Mecouch, W. J.; Reitmeier, Z. J.; Park, J.-S.; Davis, R. F.; Sitar, Z.

2005-05-01

413

Greyscale proton beam writing in p-type Gallium Arsenide  

NASA Astrophysics Data System (ADS)

Proton beam writing (PBW) is a well known method for micromachining, e.g. of semiconductors. Up to now, only few indication is given on how the resulting structure height in micromachined semiconductors can be controlled by means of fluence variation. This approach for 3D-microstructuring, called Greyscale PBW, was already successfully demonstrated for negative photoresists. In this study (1 0 0) p-type Gallium Arsenide (GaAs) was irradiated with 2.28 MeV protons and fluences in the range from 1.2×1014 H+ cm-2 to 1.0×1018 H+ cm-2 at the ion beam laboratory LIPSION and subsequently electrochemically etched with 10%-KOH. A linear dependency of structure height on ion fluence was established. In this way, pyramid-like structures as well as concave-shaped structures could be created. GaAs showed a lateral anisotropic etch behaviour during the development step with preferential etching along the [0 1 1] directions. On some structures the surface roughness and the change of conductivity were investigated by atomic force and scanning capacitance microscopy, respectively. The rms roughness of the surface of the structures was 5.4 nm and 10.6 nm for a fluence of 7.8×1015 H+ cm-2 and 1.2×1017 H+ cm-2, respectively. We observed an increasing etching rate for fluences larger than 1016 H+ cm-2.

Diering, D.; Spemann, D.; Lenzner, J.; Müller, St.; Böntgen, T.; von Wenckstern, H.

2013-07-01

414

Analytic bond-order potential for the gallium arsenide system  

NASA Astrophysics Data System (ADS)

An analytic, bond-order potential (BOP) is proposed and parametrized for the gallium arsenide system. The potential addresses primary (?) and secondary (?) bonding and the valence-dependent character of heteroatomic bonding, and it can be combined with an electron counting potential to address the distribution of electrons on the GaAs surface. The potential was derived from a tight-binding description of covalent bonding by retaining the first two levels of an expanded Green’s function for the ? and ? bond-order terms. Predictions using the potential were compared with independent estimates for the structures and binding energy of small clusters (dimers, trimers, and tetramers) and for various bulk lattices with coordinations varying from 4 to 12. The structure and energies of simple point defects and melting transitions were also investigated. The relative stabilities of the (001) surface reconstructions of GaAs were well predicted, especially under high-arsenic-overpressure conditions. The structural and binding energy trends of this GaAs BOP generally match experimental observations and ab initio calculations.

Murdick, D. A.; Zhou, X. W.; Wadley, H. N. G.; Nguyen-Manh, D.; Drautz, R.; Pettifor, D. G.

2006-01-01

415

Vibrational dynamics of liquid gallium at 320 and 970 K  

SciTech Connect

The microscopic ion dynamics of liquid gallium was investigated at 320 K--that is, just above the melting point--and 970 K by inelastic neutron scattering experiments and molecular dynamics simulations. The high quality of the experimental data allowed the observation of density fluctuation modes extending up to 1.0 A{sup -1} and existing at both temperatures. At melting, an acousticlike mode propagating with a velocity definitely exceeding the sound velocity was observed, in agreement with the results of a recent inelastic x-ray scattering experiment. The mode velocity and damping were found to be almost temperature independent. The experimental response function was compared with the results of a molecular dynamics simulation, based on a simple model for the effective ion-ion potential which, however, did not contain any temperature-dependent parameter. The result worth noting is that, despite the simple potential, the simulation was capable to reproduce all the observed features of the measured dynamicstructure factor quantitatively and at both the temperatures.

Bove, L.E.; Formisano, F. [INFM, Operative Group Grenoble, F-38042 Grenoble Cedex 09 (France); Sacchetti, F.; Petrillo, C. [INFM and Dipartimento di Fisica, Universita di Perugia, I-06123 Perugia (Italy); Ivanov, A.; Dorner, B. [Institut Laue Langevin, BP 156, F-38042 Grenoble Cedex 9 (France); Barocchi, F. [INFM and Dipartimento di Fisica, Universita di Firenze, I-50019 Florence (Italy)

2005-01-01

416

Deprotecting thioacetyl-terminated terphenyldithiol for assembly on gallium arsenide.  

PubMed

We characterize the assembly of terphenyldithiol (TPDT) on gallium arsenide (GaAs) from ethanol (EtOH) and tetrahydrofuran (THF) as a function of ammonium hydroxide (NH4OH) concentration. NH4OH facilitates the conversion of thioacetyl end groups of the TPDT precursor to thiolates in the assembly solution. The final structure of TPDT assembled on GaAs is sensitive not only to the assembly solvent but also to NH4OH concentration. In the presence of low concentrations of NH4OH (1 mM), TPDT assemblies from EtOH are oriented upright. The same assemblies are less upright when adsorption is carried out at higher NH4OH concentrations. In THF, TPDT does not adsorb significantly on GaAs at low NH4OH concentrations. The surface coverage and structural organization of these assemblies improve with increasing NH4OH concentrations, although these assemblies are never as organized as those from EtOH. The difference in the final structure of TPDT assemblies is attributed to differences in the thiolate fraction in the assembly solution at the point of substrate immersion. PMID:18163654

Krapchetov, Dmitry A; Ma, Hong; Jen, Alex K Y; Fischer, Daniel A; Loo, Yueh-Lin

2008-02-01

417

Epitaxial Zinc Oxide Semiconductor Film deposited on Gallium Nitride Substrate  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) is a wide bandgap semiconductor which is very promising for making efficient electronic and optical devices. The goal of this research was to produce high quality ZnO film on gallium nitride (GaN) substrate by optimizing the substrate temperature. The GaN substrates were chemically cleaned and mounted on a ceramic heater and loaded into a vacuum deposition chamber that was pumped down to a base pressure of 3 x 10-7 Torr. The film deposition was preceded by a 30 minute thermal desorption carried in vacuum at 500 ^oC. The ZnO thin film was then sputter-deposited using an O2/Ar gas mixture onto GaN substrates heated at temperatures varying from 20 ^oC to 500 ^oC. Post-deposition annealing was done in a rapid thermal processor at 900 ^oC for 5 min in an ultrapure N2 ambient to improve the crystal quality of the films. The films were then optically characterized using photoluminescence (PL) measurement with a UV laser excitation. Our measurements reveal that ZnO films deposited on GaN substrate held at 200 ^oC gave the best film with the highest luminous intensity, with a peak energy of 3.28 eV and a full width half maximum of 87.4 nm. Results from low temperature (10 K) PL measurements and from x-ray diffraction will also be presented.

McMaster, Michael; Oder, Tom

2011-04-01

418

Promises and failures of gallium as an antibacterial agent.  

PubMed

Gallium has a long history as a diagnostic and chemotherapeutic agent. The pharmacological properties of Ga(III) rely on chemical mimicry; when Ga(III) is exogenously supplied to living cells it can replace Fe(III) within target molecules, thereby perturbing bacterial metabolism. Ga(III)-induced metabolic distresses are dramatic in fast-growing cells, like bacterial cells. Interest in the antibacterial properties of Ga(III) has been raised by the compelling need for novel drugs to combat multidrug-resistant bacteria and by the shortage of new antibiotic candidates in the pharmaceutical pipeline. Ga(III) activity has been demonstrated, both in vitro and in animal models of infections, on several bacterial pathogens, also including intracellular and biofilm-forming bacteria. Ga(III) activity is affected by iron availability and the metabolic state of the cell, being maximal in iron-poor media and in respiring cells. Synergism between Ga(III) and antibiotics holds promise as last resort therapy for infections sustained by pandrug-resistant bacteria. PMID:24762310

Minandri, Fabrizia; Bonchi, Carlo; Frangipani, Emanuela; Imperi, Francesco; Visca, Paolo

2014-03-01

419

Optical Properties of Gallium-Doped Zinc Oxide-A Low-Loss Plasmonic Material: First-Principles Theory and Experiment  

NASA Astrophysics Data System (ADS)

Searching for better materials for plasmonic and metamaterial applications is an inverse design problem where theoretical studies are necessary. Using basic models of impurity doping in semiconductors, transparent conducting oxides (TCOs) are identified as low-loss plasmonic materials in the near-infrared wavelength range. A more sophisticated theoretical study would help not only to improve the properties of TCOs but also to design further lower-loss materials. In this study, optical functions of one such TCO, gallium-doped zinc oxide (GZO), are studied both experimentally and by first-principles density-functional calculations. Pulsed-laser-deposited GZO films are studied by the x-ray diffraction and generalized spectroscopic ellipsometry. Theoretical studies are performed by the total-energy-minimization method for the equilibrium atomic structure of GZO and random phase approximation with the quasiparticle gap correction. Plasma excitation effects are also included for optical functions. This study identifies mechanisms other than doping, such as alloying effects, that significantly influence the optical properties of GZO films. It also indicates that ultraheavy Ga doping of ZnO results in a new alloy material, rather than just degenerately doped ZnO. This work is the first step to achieve a fundamental understanding of the connection between material, structural, and optical properties of highly doped TCOs to tailor those materials for various plasmonic applications.

Kim, Jongbum; Naik, Gururaj V.; Gavrilenko, Alexander V.; Dondapati, Krishnaveni; Gavrilenko, Vladimir I.; Prokes, S. M.; Glembocki, Orest J.; Shalaev, Vladimir M.; Boltasseva, Alexandra

2013-12-01

420

Interaction of InGa liquid alloy coolant with gold coated optical materials  

SciTech Connect

A significant reaction is reported between gold surfaces and an indium-gallium eutectic liquid alloy often used to transfer heat away from optical elements in high power synchrotron radiation beamlines. This reaction proceeds at the slightly elevated temperatures (70{degrees}C) typical of conservative bakeouts used to achieve ultrahigh vacuum in the chambers which house these optical elements (mirrors, gratings, and crystals) without damaging their highly precise figure and finish. The nature and extent of this reaction is discussed, based mostly on the experience gained recently during the vacuum commissioning of two mirror chambers for a VUV wiggler-based synchrotron radiation beamline. 2 refs., 5 figs.

Hulbert, S.L.

1991-01-01

421

Defect behavior in electron-irradiated boron- and gallium-doped silicon  

NASA Technical Reports Server (NTRS)

Production and anneal of defects in electron-irradiated, float-zone silicon solar cells were studied by DLTS. In boron- and gallium-doped, n+-p cells, dominant defects were due to the divacancy, carbon interstitial, and carbon complex. Results suggest that the DLTS peak normally ascribed to carbon complexes also involves gallium. For gallium- and, to a lesser extent, boron-doped samples, damaged lifetime shows substantial recovery only when the carbon-complex peak has annealed out at 400 C. In boron-doped, n+-p-p+ cells, a minority carrier trap (E1) was also observed by DLTS in cells with a boron p+, but not in those with an aluminum p+ back. A level at Ev + 0.31 eV appeared upon 150 C annealing (E1 out) in both p+ back types of samples.

Drevinsky, P. J.; Deangelis, H. M.

1982-01-01

422

Piecewise simulaton proton test of gallium arsenide and thin silicon solar cells  

NASA Technical Reports Server (NTRS)

Gallium Arsenide (GaAs) solar cells are viewed as a potential primary power source on certain future Earth orbiting satellites. However, the relative merits of gallium arsenide over silicon in a space radiation environment are largely unknown because a general degradation model for gallium arsenide does not exist. The results of a test simulating the proton radiation environment existing in a polar orbit and the concomitant effects on GaAs and thin silicon (Si) solar cells are presented. The objectives and methodology of the simulation test were discussed. The electrical characteristics of GaAs and Si solar cells are given in graph form. It was concluded that GaAs cells are viable for use on satellites in low Earth orbit.

Peterson, D. G.; Billets, S. A.

1984-01-01

423

Pre-treatment with EDTA-gallium prevents the formation of biofilms on surfaces  

PubMed Central

Pseudomonas aeruginosa and Streptococcus pyogenes are leading causes of medical device-associated infections. The capacity to establish and maintain these infections is thought to be associated with the ability to form surface-attached biofilms. In the present study, gallium nitrate was used to coat PVC plates and biofilm formation on the plates by Pseudomonas aeruginosa and Streptococcus pyogenes was evaluated. The results demonstrated that coating the PVC surface with gallium reduced bacteria cell aggregation on the PVC surface and inhibited biofilm formation. These results suggest that surface pre-treatment with a gallium nitrate coating is a potential strategy for the prevention of infections associated with Pseudomonas aeruginosa or Streptococcus pyogenes on medical devices.

ZHU, YUANYUAN; JIN, FENG; YANG, SHUANGWANG; LI, JINGNONG; HU, DAN; LIAO, LIANMING

2013-01-01

424

Use of tricatecholamide ligands to alter the biodistribution of gallium-67: concise communication.  

PubMed

The effect of the intravenous administration of the synthetic siderophore LI-CAM-C on the biodistribution of Ga-67 was investigated. The ligand was found capable of the in vivo complexing with Ga-67, which hastened the renal clearance of the nuclide. The gallium concentration was decreased in all organs, with the exception of the liver and spleen, where we suggest that hydroxide precipitates interfere with gallium sequestration by LICAM-C. The gallium in abscess tissue was only slightly affected, giving rise to an increase in the Ga-67 abscess-to-soft-tissue concentration ratio when LICAM-C is administered. Dosimetry calculations show that the siderophore decreases the radiation burden from Ga-67 citrate. The advantage of clinical application of LICAM-C are discussed. PMID:6951964

Moerlein, S M; Welch, M J; Raymond, K N

1982-06-01

425

Demonstration of surface-enhanced Raman scattering by tunable, plasmonic gallium nanoparticles  

PubMed Central

Size-controlled gallium nanoparticles deposited on sapphire are explored as alternative substrates to enhance Raman spectral signatures. Gallium’s resilience following oxidation is inherently advantageous compared to silver for practical ex vacuo, non-solution applications. Ga nanoparticles are grown using a simple, molecular beam epitaxy-based fabrication protocol, and by monitoring their corresponding surface plasmon resonance energy through in situ spectroscopic ellipsometry, the nanoparticles are easily controlled for size. Raman spectroscopy performed on cresyl fast violet (CFV) deposited on substrates of differing mean nanoparticle size represents the first demonstration of enhanced Raman signals from reproducibly tunable self-assembled Ga nanoparticles. Non-optimized aggregate enhancement factors of ~80 were observed from the substrate with the smallest Ga nanoparticles for CFV dye solutions down to a dilution of 10 ppm.

Wu, Pae C; Khoury, Christopher G.; Kim, Tong-Ho; Yang, Yang; Losurdo, Maria; Bianco, Giuseppe V.; Vo-Dinh, Tuan; Brown, April S.; Everitt, Henry O.

2009-01-01

426

Crystal chemistry and self-lubricating properties of monochalcogenides gallium selenide and tin selenide  

SciTech Connect

This paper describes the fundamentals of the crystal chemistry and self-lubricating mechanisms of two monochalcogenides; tin selenide and gallium selenide. Specifically, it enumerates their inter-atomic array and bond structure in crystalline states, and correlates this fundamental knowledge with their self-lubricating capacity. Friction tests assessing the self-lubricating performance of gallium and tin selenides were carried out on a pin-on-disk machine. Specifically, large crystalline pieces of gallium selenide and tin selenide were cut and cleaved into flat squares and subsequently rubbed against the sapphire balls. In another case, the fine powders (particle size {approx} 50--100 {mu}m) of gallium selenide and tin selenide were manually fed into the sliding interfaces of 440C pins and 440C disks. For the specific test conditions explored, it was found that the friction coefficients of the sapphire/gallium selenide and sapphire/tin selenide pairs were {approx} 0.23 and {approx} 0.35, respectively. The friction coefficients of 440C pin/440C disk test pairs with gallium selenide and tin selenide powders were on the orders of {approx} 0.22 and {approx} 0.38, respectively. For comparison, a number of parallel friction tests were performed with MoS{sub 2} powders and compacts and the results of these tests were also reported. The friction data together with the crystal-chemical knowledge and the electron microscopic evidence supported the conclusion that the lubricity and self-lubricating mechanisms of these solids are closely related to their crystal chemistry and the nature of interlayer bonding.

Erdemir, A.

1993-02-01

427

Advanced battery grid alloys  

Microsoft Academic Search

The alloys used in lead-acid batteries have changed markedly during the past five years. The problems in casting lead-calcium alloys have been overcome by the addition of aluminum to the alloys. The aluminum protects the alloys and prevents loss of calcium, yielding greatly improved grain structures and corrosion resistance. Concern about reduced water loss has led to a dramatic reduction

Prengaman

1984-01-01

428

Total neutron scattering investigation of the structure of a cobalt gallium oxide spinel prepared by solvothermal oxidation of gallium metal  

NASA Astrophysics Data System (ADS)

A new solvothermal synthesis route to mixed-metal gallium oxides with the spinel structure has been developed for ternary oxides of ideal composition Ga3-xMxO4-y (M=Co, Zn, Ni). The structure of the novel cobalt gallate produced in this manner, Ga1.767(8)Co0.973(8)O3.752(8), has been determined from total neutron scattering to be a partially defective spinel with mixed-valent cobalt (approximately 25% Co3+ and 75% Co2+) and with vacancies on approximately 6% of oxygen sites. Pair distribution function (PDF) analysis reveals significant local deviations from the average cubic structure, which are attributed to the conflicting coordination preferences of the Co2+ (potential Jahn-Teller distortion) and Ga3+ (Ga off-centring). Reverse Monte Carlo (RMC) modelling supports this conclusion since different metal-oxygen bond-distance distributions are found for the two cations in the refined configuration. An investigation of magnetic properties shows evidence of short-range magnetic order and spin-glass-like behaviour, consistent with the structural disorder of the material.

Playford, Helen Y.; Hannon, Alex C.; Tucker, Matthew G.; Lees, Martin R.; Walton, Richard I.

2013-11-01

429

Novel ethylenediamine-gallium phosphate containing 6-fold coordinated gallium atoms with unusual four equatorial Ga-N bonds  

NASA Astrophysics Data System (ADS)

A novel ethylenediamine-gallium phosphate, formulated as Ga(H2NCH2CH2NH2)2PO4·2H2O, was synthesized under hydrothermal conditions. The crystal structure, including hydrogen positions, was determined using single-crystal X-ray diffraction data (monoclinic, a=9.4886(3) Å, b=6.0374(2) Å, c=10.2874(3) Å, and ?=104.226(3)°, space group Pc) and the bulk was characterized by chemical (Ga-P-C-H-N) and thermal analysis (TG-MS and DSC), including activation energy data of its thermo-oxidative degradation, powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (SS-NMR) measurements, and transmission electron microscopy (TEM, SAED/NBD, and STEM BF-EDX). The crystal structure is built up of infinite zig-zag chains running along the c-axis, formed by vertex-shared {PO4} and {GaO2N4} polyhedra. The new compound is characterized by unusual four equatorial Ga-N bonds coming from two nonequivalent ethylenediamine molecules and exhibits strong blue emission at 430 nm (?ex=350 nm) in the solid state at room temperature.

Torre-Fernández, Laura; Espina, Aránzazu; Khainakov, Sergei A.; Amghouz, Zakariae; García, José R.; García-Granda, Santiago

2014-07-01

430

Gallium diffusion into self-assembled InAs quantum dots grown on indium phosphide substrates  

SciTech Connect

The photoluminescence spectrum of small self-assembled In(Ga)As quantum dots grown on InP substrates is composed of distinct spectral lines. These lines correspond to monolayer variations in the dots smallest dimension: their heights. We use this phenomenon in order to study the diffusion of gallium atoms into the self-assembled quantum dots. We demonstrate that substantial amounts of gallium atoms diffuse from a strained GaInP layer underneath the quantum dots into the quantum dots.

Raz, T.; Shuall, N.; Bahir, G.; Ritter, D.; Gershoni, D.; Chu, S.N.G. [Department of Electrical Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 32000 (Israel); Physics Department and The Solid State Institute, Technion - Israel Institute of Technology, Technion City, Haifa 32000 (Israel); Multiplex, Inc., 5000 Hadley Rd., South Plainfield, New Jersey 07080 (United States)

2004-10-18

431

Plasma Synthesis of Light Emitting Gallium Nitride Nanoparticles Using a Novel Microwave-Resonant Cavity  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) based light-emitting nanoparticles were synthesized by microwave plasma chemical vapor synthesis under slightly reduced pressure condition. A novel 2.45 GHz microwave resonant cavity was developed that facilitated the ignition and stable operation. The cavity was designed with the aid of electromagnetic field simulations to match the microwaves in the transverse magnetic (TM) 010-like mode before plasma ignition and in a transverse electromagnetic (TEM)-like mode after plasma ignition. The produced nanoparticles were amorphous and emitted light at the same wavelength as bulk gallium nitride.

Shimada, Manabu; Azuma, Yasushi; Okuyama, Kikuo; Hayashi, Yutaka; Tanabe, Eiji

2006-01-01

432

Recovery of gallium and arsenic from GaAs wafer manufacturing slurries  

SciTech Connect

Lapping and polishing slurries from the gallium arsenide (GaAs) wafer manufacturing process were used to develop simple and inexpensive methods for separation and recovery of valuable gallium and toxic arsenic. The lapping slurry, containing GaAs, glycerol, alumina, iron oxide, and water, is treated by a process involving water addition, dissolution of GaAs, mixing, sedimentation, decantation, and evaporation. The polishing slurry, containing GaAs, silica, sodium bicarbonate, sodium hypochlorite and water, is treated simply by a repetitive cycle of adding water, mixing, settling, decanting, and evaporating. After treatment, the slurries contain less than 5 ppm of dissolved arsenic and are considered non-hazardous.

Jadvar, R.; McCoy, B.J. (Univ. of California, Davis (United States)); Ford, B.; Galt, J. (Harris Microwave Semiconductor, Inc., Milpitas, CA (United States))

1991-11-01

433

Patterns of gallium-67 scintigraphy in patients with acquired immunodeficiency syndrome and the AIDS related complex  

SciTech Connect

Thirty-two patients with AIDS related complex (ARC) or acquired immunodeficiency syndrome (AIDS) underwent /sup 67/Ga scans as part of their evaluation. Three patterns of /sup 67/Ga biodistribution were found: lymph node uptake alone; diffuse pulmonary uptake; normal scan. Gallium-67 scans were useful in identifying clinically occult Pneumocystis carinii pneumonia in seven of 15 patients with ARC who were asymptomatic and had normal chest radiographs. Gallium scans are a useful ancillary procedure in the evaluation of patients with ARC or AIDS.

Bitran, J.; Bekerman, C.; Weinstein, R.; Bennett, C.; Ryo, U.; Pinsky, S.

1987-07-01

434

A unique finding on gallium-67 scintigraphy: widespread fatal skin manifestations of Pseudomonas sepsis.  

PubMed

We report a case of a 25-year-old woman presented with neutropenic fever after chemotherapy for the relapse of acute biphenotypic leukemia. Gallium-67 scintigraphy for the detection of infectious foci demonstrated a unique pattern of numerous foci with intense and varying-sized radioactivity spreading throughout the body. The subsequent skin biopsy and culture proved Pseudomonas infection. Therefore, this unique image, in combination with clinical information, was compatible with cutaneous manifestations of Pseudomonas sepsis. Eventually, the patient died of uncontrolled systemic infection despite the aggressive antibiotic treatment. This case reminded clinicians and nuclear medicine physicians to notice the potentially fatal finding on gallium-67 scan. PMID:21716010

Wu, Yu-Chin; Hsieh, Te-Chun; Sun, Shung-Shung; Lo, Woei-Chung; Yen, Kuo-Yang; Kao, Chia-Hung

2011-08-01

435

Thyroiditis mimicking relapse of acute lymphoblastic leukemia: Gallium-67 scan suggested the diagnosis  

PubMed Central

Acute lymphoblastic leukemia (ALL) is the most common form of leukemia in childhood and accounts for 85% of cases. ALL frequently presents as an infectious process with an abrupt onset of high fever. Thyroid disease has been reported to have a strong association with acute leukemia. Gallium (Ga-67) citrate has been used in the investigation of patients labeled as having pyrexia of unknown origin. We report a case of a 13-year-old female patient who presented with fever and suspected disease relapse after a period of disease remission; however, gallium-67 citrate whole body scan suggested the diagnosis of thyroiditis.

Othman, Saleh

2010-01-01

436

Structure and properties of a Pu-0.18 wt.% Ga alloy  

NASA Astrophysics Data System (ADS)

This study describes the characterisation of a cast plutonium-0.18 wt.% gallium (Pu-0.18 wt.% Ga) alloy, both in the as-cast condition as well as following an homogenising heat treatment. The alloy was subjected to density measurements, differential scanning calorimetry (DSC), dilatometry, optical microscopy, electron probe micro-analysis (EPMA), X-ray diffraction (XRD) and hardness measurements. The Ga content is insufficient to retain a wholly delta phase at ambient temperature. Instead, the alloy appears to be a mixture of alpha- and delta-Pu, which is borne out by density, dilatometry, DSC and XRD. Optical microscopy of the alloy following heat treatment revealed the microstructure to be composed of a two-phase mixture of alpha-Pu (?-Pu) and delta-Pu (?-Pu). EPMA of the heat treated alloy shows the Ga content to be evenly distributed throughout the microstructure. The hardness of the heat treated alloy is approximately 25% lower than that of unalloyed Pu. No evidence supporting the presence of an amorphous Pu phase has been found.

Wheeler, D. W.; Jenkins, R. F. E.; Gover, R. K. B.; Matthews, M. B.; Roussel, P.

2013-09-01

437

Electrical activation studies of ion implanted gallium nitride  

NASA Astrophysics Data System (ADS)

A comprehensive and systematic electrical activation study of Si-implanted gallium nitride (GaN) was performed as a function of ion implantation dose, anneal temperature, and implantation temperature. Additionally, Mg-implanted GaN was also investigated. Temperature-dependent Hall effect measurements and photoluminescence (PL) spectra were used to characterize the samples. GaN wafers capped with AlN were implanted at room temperature and at 800°C with 200 keV Si ions at doses ranging from 1 x 1013 to 5 x 1015 cm-2 and annealed from 1050 to 1350°C for 5 min to 17 sec in flowing nitrogen. The optimum anneal temperature for samples implanted with the higher Si doses is around 1350°C, exhibiting nearly 100% electrical activation efficiency. Exceptional mobilities and carrier concentrations were obtained on all Si implanted samples. PL spectra revealed nearly complete implantation damage recovery as well as the nature of the yellow luminescence plaguing nearly all Si-doped GaN. Additionally, GaN wafers were implanted with Mg and various coimplants and annealed from 1100 to 1350°C. All of the Mg-implanted and most of the Mg coimplanted GaN samples became extremely resistive, and did not show definite p-type conductivity even after annealing at 1350°C, remaining highly resistive even at a sample temperature as high as 800 K. A dominant 2.36 eV green luminescence band observed in the PL spectra of all Mg implanted samples is attributed to a Mg-related deep complex DAP transition. The inefficient electrical activation of Mg acceptors implanted into GaN is attributed to these Mg-related deep complexes.

Fellows, James Andrew

438

Anticancer activity of dinuclear gallium(III) carboxylate complexes.  

PubMed

The reaction of 3-methoxyphenylacetic acid, 4-methoxyphenylacetic acid, mesitylthioacetic acid, 2,5-dimethyl-3-furoic acid and 1,4-benzodioxane-6-carboxylic acid with trimethylgallium (1:1) yielded the dimeric complexes [Me(2)Ga(micro-O(2)CCH(2)C(6)H(4)-3-OMe)](2) (1), [Me(2)Ga(micro-O(2)CCH(2)C(6)H(4)-4-OMe)](2) (2), [Me(2)Ga(micro-O(2)CCH(2)SMes)](2) (3) (Mes=2,4,6-Me(3)C(6)H(2)), [Me(2)Ga{micro-O(2)C(Fur)}](2) (4) (Fur=2,5-dimethylfuran) and [Me(2)Ga{micro-O(2)C(Bdo)}](2) (5) (Bdo=1,4-benzodioxane) respectively. The molecular structure of 5 was determined by X-ray diffraction studies. The cytotoxic activity of the gallium(III) complexes (1-5) was tested against human tumor cell lines 8505C anaplastic thyroid cancer, A253 head and neck tumor, A549 lung carcinoma, A2780 ovarian cancer, DLD-1 colon carcinoma and compared with that of cisplatin. Taking into account the standard deviation, there is no significant difference in the activity for any of the compounds in any cell line. However, complex 5 presents the best IC(50) value against A253 head and neck tumor (6.6+/-0.2 microM), while complex 3 seems to be the most active against A2780 ovarian cancer (12.0+/-0.4 microM) and marginally on DLD-1 colon carcinoma (12.4+/-0.1 microM). PMID:19926362

Kaluderovi?, Milena R; Gómez-Ruiz, Santiago; Gallego, Beatriz; Hey-Hawkins, Evamarie; Paschke, Reinhard; Kaluderovi?, Goran N

2010-02-01

439

Indium Phosphide Window Layers for Indium Gallium Arsenide Solar Cells  

NASA Technical Reports Server (NTRS)

Window layers help in reducing the surface recombination at the emitter surface of the solar cells resulting in significant improvement in energy conversion efficiency. Indium gallium arsenide (In(x)Ga(1-x)As) and related materials based solar cells are quite promising for photovoltaic and thermophotovoltaic applications. The flexibility of the change in the bandgap energy and the growth of InGaAs on different substrates make this material very attractive for multi-bandgap energy, multi-junction solar cell approaches. The high efficiency and better radiation performance of the solar cell structures based on InGaAs make them suitable for space power applications. This work investigates the suitability of indium phosphide (InP) window layers for lattice-matched In(0.53)Ga(0.47)As (bandgap energy 0.74 eV) solar cells. We present the first data on the effects of the p-type InP window layer on p-on-n lattice-matched InGaAs solar cells. The modeled quantum efficiency results show a significant improvement in the blue region with the InP window. The bare InGaAs solar cell performance suffers due to high surface recombination velocity (10(exp 7) cm/s). The large band discontinuity at the InP/InGaAs heterojunction offers a great potential barrier to minority carriers. The calculated results demonstrate that the InP window layer effectively passivates the solar cell front surface, hence resulting in reduced surface recombination and therefore, significantly improving the performance of the InGaAs solar cell.

Jain, Raj K.

2005-01-01

440

Asynchronous techniques for digital MESFET gallium arsenide circuits  

NASA Astrophysics Data System (ADS)

There are many applications where ultra-fast digital arithmetic circuits are required. At ultra-high speeds a considerable part of power is dissipated within a clock generation and distribution syste. At the same time, at gigahertz frequencies the clock skew becomes a factor limiting the speed of the system. This paper presents a design methodology for highly pipelined, self-timed circuits and systems suitable for multimedia applications using Gallium Arsenide MESFET as the base technology implementation of latched logic design style (PDLL, LCFL). The use of latched logic together with the absence of the global clock provides for low power dissipation while maintaining very high speed of the system. The main advantage of the latched structure is provided by the feedback which ensures that the nose margin is higher than for a simple Direct Coupled FET Logic gate. This enables to use serial connections of the E-type transistors in the pull-down section. Therefore, in GaAs latched logic it is possible to implement logic gates based on the AND function which have several control inputs and that they generate at least one control signal for handshaking. For the typical 4- phase handshaking protocol the input signals are enable and start and the required generated signal is Done. In the paper the appropriate modifications of the handshaking protocol to accommodate the properties of the latched logic GaAs circuits is presented an the inherent latching property of LCFL is exploited to eliminate latches separate from the logic blocks in the classic pipeline. Several circuit examples demonstrate the advantages of the proposed circuit techniques.

Eshraghian, Kamran; Lachowicz, Stefan

1999-10-01